Bcaa ratio of amino acids. Optimal BCAA ratio. The importance of amino acids in bodybuilding

It's time to find out what amino acids are, what they are needed for and how to take them correctly.

Amino acids serve as “building materials” for proteins, since thanks to the unique sequence of 21 types of these organic compounds, all types of proteins and muscle tissue are formed in the body. In terms of chemical structure, amino acids are characterized by the presence of an amino group with a nitrogen atom, which is the basis of this compound.

The presence of a nitrogen atom distinguishes amino acids from other nutrients we get from food (such as carbohydrates), which is why they are the only compounds that are able to form tissues, organs, muscles, skin and hair.

Nowadays, when people hear about protein, they automatically think only about muscles and bodybuilding, although amino acids are a significant component of any person's diet, but it is especially important for those who play any kind of sport. Amino acids are generally divided into 3 categories: essential, semi-essential and non-essential.

What is meant by the word “irreplaceable”? “Essential” means that these amino acids cannot be synthesized in the body and must be obtained from food. There are 9 essential amino acids, including the famous BCAA group.

Branched Chain Amino Acids (BCAAs)

Leucine, isoleucine and valine

Of the 9 essential amino acids, 3 are classified as branched chain amino acids. These are leucine, isoleucine and valine. BCAAs have a unique chemical structure compared to other essential amino acids, and therefore have special properties. Unlike other amino acids, BCAAs are absorbed faster and better by the body, that is, they are not absorbed in the stomach, but actually go directly to the muscles. To learn more about BCAA, read our article “BCAA. What are branched chain amino acids?

Other essential amino acids

The remaining essential amino acids: histidine, methionine, phenylalanine, threonine, tryptophan and lysine are required by the body to perform a number of physiological functions.

Histidine

Histidine is an aromatic amino acid that performs a number of vital functions in the body, including participation in the synthesis of hemoglobin, the functioning of the immune system and tissue repair. Histidine is an important amino acid during human growth, as well as during rehabilitation after illness.

Lysine

Lysine plays an important role in the functioning of the immune system. It also, along with semi-essential acids, is involved in the synthesis of collagen so that the skin, hair and nails remain healthy.

Tryptophan

Tryptophan is an essential aromatic amino acid that contains an indole core. It performs a number of functions in the body, in particular playing the role of a chemical messenger in the nervous system. Unlike other amino acids, L-tryptophan is not soluble in water and is heat resistant, meaning it does not lose most of its beneficial properties during processing.

Methionine

Methionine is a foul-smelling amino acid (contains a sulfur atom) that is a precursor to other amino acids such as taurine. Its antioxidant properties can protect the body by suppressing the effects of harmful substances. It is also involved in the construction of proteins and the production of various hormones, including adrenaline and melatonin.

Phenylalanine

Phenylalanine is a non-polar amino acid that has a benzyl side chain and is known for its antidepressant properties. It plays an important role in the production of dopamine and adrenaline.

Threonine

This amino acid is polar, uncharged, and once absorbed is converted to pyruvate, playing an important role in glucose production and ATP energy production.

Nonessential amino acids

Nonessential amino acids are those that can be synthesized by the body. You may have the following question: “If they are produced in the body, then why do we need to take them additionally?” The fact is that during physical exercise, after the energy in the form of carbohydrates is exhausted, the body begins to look for other sources of nutrition. Amino acids can act as such a source to provide the muscles with everything they need to continue training. However, the body is often unable to produce amino acids quickly enough to meet increased demands during exercise, so we must consume more of them, regardless of whether they are essential or not.

Alanin

Alanine is one of the simplest organic compounds in terms of chemical structure and is classified as a non-polar amino acid. Alanine plays a key role in the glucose-alanine cycle between the liver and body tissues. Simply put, it reacts in tissues to form pyruvate and then glucose to be used as an energy source.

Glycine

Glycine is the smallest of all amino acids and is associated with the production of collagen, as well as proline and lysine. In addition, it acts as a neurotransmitter in the spinal cord, brain stem and retina.

Aspartic acid

This amino acid is involved in the urea cycle in the body, as well as in a process called gluconeogenesis (the metabolic pathway that leads to the formation of glucose). In addition, aspartic acid acts as a neurotransmitter that stimulates certain receptors in the nervous system.

Asparagine

Asparagine is necessary for the normal functioning of the nervous system, and it also plays an important role in the synthesis of ammonia.

Semi-essential or conditionally essential amino acids

These amino acids can be produced by the body in certain amounts, but in some circumstances this amount is not sufficient for normal physiological functioning, such as during illness or intense exercise.

Serin

Serine is a proteinogenic amino acid that performs a number of biological functions in the body. It plays an important role in metabolism, enzymatic reactions and brain function.

Arginine

Arginine is a precursor of nitric oxide. It reduces recovery time after injuries, accelerates the healing of damaged tissue and helps reduce and stabilize blood pressure.

Tyrosine

Tyrosine is a proteinogenic amino acid that plays an important role in cell signaling.

Proline

This amino acid has an exceptionally rigid structure that is used to synthesize collagen, which is essential for maintaining healthy hair, skin and nails.

Ornithine

Ornithine plays a key role in urea biosynthesis and is also thought to prevent fatigue during exercise. The urea cycle is a series of biochemical processes that produce urea to remove ammonia from the body.

Glutamine

Glutamine is one of the most popular semi-essential amino acids among athletes, which is involved in regulating acidity in the kidneys, creating cellular energy and stimulating muscle metabolism.

Cysteine

Cysteine ​​plays an important role in enzymatic reactions in the body. It is believed to be involved in metal binding and is also a precursor to certain antioxidants.

Benefits and uses of amino acids

Now let’s figure out what amino acids are needed for and for what purposes they are effective. Amino acids are an integral part of our body and the processes that occur in it every day. Maintaining proper amino acid balance through supplementation has demonstrated great benefits to the body, from stimulating muscle growth to improving immune system function.

1. Muscle anabolism, reducing muscle fatigue and aiding muscle recovery

The greatest benefit of amino acid supplementation is its ability to stimulate muscle anabolism, repair muscles, and prevent the onset of muscle fatigue.

Leucine, isoleucine, valine, asparagine, aspartic acid and glutamine are the 6 amino acids that are metabolized in muscles at rest. They support numerous metabolic processes, for example, they play a fundamental role as substrates for protein synthesis and energy production, and are also a precursor to glutamine and alanine.

During the first 10 minutes of exercise, the body undergoes a reaction involving the enzyme alanine aminotransferase to maintain high levels of certain amino acids during exercise. Intermediates that are formed as a result of this reaction can cause fatigue. However, glutamine has a number of functions in the body that allow it to be used as a nutritional source, which is why glutamine supplements can increase muscle energy and muscle metabolic rate during exercise.

These beneficial properties of amino acid supplements make them ideal not only for bodybuilders, but also for runners, sprinters, and people leading an active lifestyle.

In 2000, an experiment was conducted to determine the response of muscle protein to amino acid intake. Six men and women drank a drink containing 6 g of essential amino acids or a placebo drink 1 hour after exercise. Those taking the amino acids saw an increase in phenylalanine levels, which did not occur among those taking the placebo. This increase caused an anabolic response in the muscles, so it was concluded that amino acids stimulate protein anabolism and protein synthesis in muscles.

Additionally, a 2003 scientific review suggested that increased levels of leucine in the body can stimulate muscle protein synthesis during catabolic states caused by dietary restriction or strenuous exercise.

1. Amino acids for weight loss

Amino acids are not only beneficial for those looking to build muscle and improve muscle recovery, but they are also shown to aid weight loss. One study looked at 2 groups of people who wanted to lose weight and change their body composition. The first group used a diet high in amino acids, while the second group was low in amino acids.

After 16 days, they found that the group taking more amino acids had lost significantly more fat and less muscle mass than the other. Overall, the evidence suggests that a diet high in protein and amino acids and low in carbohydrates produces greater fat loss while maintaining protein in the body.

1. Diabetes

Diabetes mellitus is a disease in which the body is unable to effectively regulate blood sugar levels and produce insulin. When we consume carbohydrates, the glucose level in the body increases. In diabetes, the body is unable to properly produce insulin to return sugar levels to normal, resulting in hyperglycemia. Amino acids have a positive effect on blood sugar levels. For example, arginine is a precursor to nitric oxide, a messenger that has a direct effect on insulin sensitivity.

1. Inflammation and arthritis

Another beneficial property of amino acids is that they can reduce the activity of inflammatory processes in the body. One study conducted in 1973 showed that amino acid esters and sulfur-containing amino acids, including cysteine ​​and methionine, are effective anti-inflammatory agents that can reduce the effects of edema and anaphylactic shock, and even reduce inflammation and improve the condition when taken adjuvant. -induced arthritis.

1. The immune system

Although this may be news to you, dietary protein or amino acid deficiencies weaken the immune system and increase susceptibility to disease. In particular, modern research shows that arginine, glutamine and cysteine ​​play an important role in the functioning of the immune system. For example, these amino acids are involved in the activation of various lymphocytes, natural killer cells and macrophages, interfere with the redox regulation of cellular functions, gene expression and lymphocyte proliferation, and also affect the production of antibodies, cytokines and other cytotoxic substances. Scientists are now finding that amino acid supplements can improve the immune system and reduce morbidity and mortality.

1. Fertility

Recent research suggests that amino acid supplements can improve fertility rates. For example, one such study involved 132 men with fertility problems. For 3 months they took supplements with amino acids and trace elements. The control group was a group of 73 men with reduced fertility (subfertility) who took a placebo. All study results of the test group showed a significant improvement in the area of ​​conception compared to the control group. Within 6 months after the end of the experiment, 34 cases of conception were recorded in the group of men taking the supplements.

I hope you no longer have any questions about why amino acids are needed; if you have, you can always ask a question in the comments.

Amino acid supplements

If you get all the nutrients you need from food, you may not need supplements. However, it is worth remembering that during training the body's need for amino acids increases, so if you train a lot and want to build muscle or lose weight, then most likely you will need supplements. There are many options for amino acids, go to any store, they can be in powder form, tablets or capsules.

Amino acids powder

Amino acids come in a variety of flavors in powder form, so you can easily add them to your favorite juice or water.

Amino acids in tablets

You don’t have a minute of free time and urgently need to take your daily dose of amino acids? Supplements in tablet form are ideal for such situations.

Keep in mind that the role of amino acids in sports nutrition is very large; the more, the better. There is no point in taking a high-carbohydrate gainer; it’s easier to buy a kilo of sugar and mix it with protein; it will be cheaper.

How to take amino acids?

Amino acid supplements are best taken in the morning, pre-workout, post-workout and before bed to reduce muscle fatigue and maximize muscle anabolism and recovery.

How to properly take amino acids of one type or another is always indicated on the can. For example, BCAA is best taken in the morning after waking up, before and after training. Take complex amino acids between meals, as well as before and after training. To properly consume other types, you need to consider what other supplements you consume.

Amino acids are the main building material of any living organism. By their nature, they are the primary nitrogenous substances of plants, which are synthesized from the soil. The structure of amino acids depends on their composition.

Amino acid structure

Each of its molecules has carboxyl and amine groups, which are connected to a radical. If an amino acid contains 1 carboxyl and 1 amino group, its structure can be indicated by the formula presented below.

Amino acids that have 1 acid and 1 alkaline group are called monoaminomonocarboxylic acids. In organisms, 2 carboxyl groups or 2 amine groups are also synthesized and whose functions are determined. Amino acids containing 2 carboxyl and 1 amine groups are called monoaminodicarboxylic, and those containing 2 amine and 1 carboxyl are called diaminomonocarboxylic.

They also differ in the structure of the organic radical R. Each of them has its own name and structure. Hence the different functions of amino acids. It is the presence of acidic and alkaline groups that ensures its high reactivity. These groups connect amino acids and form a polymer - protein. Proteins are also called polypeptides because of their structure.

Amino acids as building materials

A protein molecule is a chain of tens or hundreds of amino acids. Proteins differ in composition, quantity and order of amino acids, because the number of combinations of 20 components is almost infinite. Some of them have the entire composition of essential amino acids, others do without one or more. Individual amino acids, a structure whose functions are similar to the proteins of the human body, are not used as food products, since they are poorly soluble and are not broken down by the gastrointestinal tract. These include the proteins of nails, hair, fur or feathers.

The functions of amino acids are difficult to overestimate. These substances are the main food in the human diet. What function do amino acids perform? They increase the growth of muscle mass, help strengthen joints and ligaments, restore damaged body tissues and participate in all processes occurring in the human body.

Essential amino acids

Only from supplements or food products can you get Functions in the process of forming healthy joints, strong muscles, beautiful hair are very significant. These amino acids include:

• phenylalanine;
• lysine;
• threonine;
• methionine;
• valine;
• leucine;
• tryptophan;
• histidine;
• isoleucine.

Functions of essential amino acids

These bricks perform essential functions in the functioning of every cell of the human body. They are invisible as long as they enter the body in sufficient quantities, but their deficiency significantly impairs the functioning of the entire body.

1. Valine renews muscles and serves as an excellent source of energy.
2. Histidine improves blood composition, promotes muscle recovery and growth, and improves joint function.
3. Isoleucine helps the production of hemoglobin. Controls the amount of sugar in the blood, increases a person’s energy and endurance.
4. Leucine strengthens the immune system, monitors the level of sugar and leukocytes in the blood. If the level of leukocytes is too high: it lowers them and activates the body’s reserves to eliminate inflammation.
5. Lysine helps absorb calcium, which builds and strengthens bones. Helps collagen production, improves hair structure. For men, this is an excellent anabolic steroid, as it builds muscles and increases male strength.
6. Methionine normalizes the functioning of the digestive system and liver. Participates in the breakdown of fats, eliminates toxicosis in pregnant women, and has a beneficial effect on hair.
7. Threonine improves the functioning of the gastrointestinal tract. Increases immunity, participates in the creation of elastin and collagen. Threonine prevents fat deposition in the liver.
8. Tryptophan is responsible for human emotions. Produces serotonin - the hormone of happiness, thereby normalizing sleep and elevating mood. Tames appetite, has a beneficial effect on the heart muscle and arteries.
9. Phenylalanine serves as a transmitter of signals from nerve cells to the brain of the head. Improves mood, suppresses unhealthy appetite, improves memory, increases sensitivity, reduces pain.

A deficiency of essential amino acids leads to stunted growth, metabolic disorders, and decreased muscle mass.

Nonessential amino acids

These are amino acids, the structure and functions of which are produced in the body:

• arginine;
• alanine;
• asparagine;
• glycine;
• proline;
• taurine;
• tyrosine;
• glutamate;
• serine;
• glutamine;
• ornithine;
• cysteine;
• carnitine

Functions of nonessential amino acids

1. Cysteine ​​eliminates toxic substances, participates in the creation of skin and muscle tissue, and is a natural antioxidant.
2. Tyrosine reduces physical fatigue, speeds up metabolism, eliminates stress and depression.
3. Alanine serves for muscle growth and is a source of energy.
4. increases metabolism and reduces ammonia formation during heavy exercise.
5. Cystine eliminates pain when ligaments and joints are injured.
6. responsible for brain activity, during prolonged physical activity it turns into glucose, producing energy.
7. Glutamine restores muscles, improves immunity, speeds up metabolism, enhances brain function and creates growth hormone.
8. Glycine is necessary for muscle function, fat breakdown, stabilization of blood pressure and blood sugar.
9. Carnitine moves fatty acids into cells, where they are broken down to release energy, resulting in the burning of excess fat and generating energy.
10. Ornithine produces growth hormone, is involved in the process of urine formation, breaks down fatty acids, and helps produce insulin.
11. Proline ensures the production of collagen, it is necessary for ligaments and joints.
12. Serine improves immunity and produces energy; it is needed for rapid metabolism of fatty acids and muscle growth.
13. Taurine breaks down fat, increases the body's resistance, and synthesizes bile salts.

Protein and its properties

Proteins, or proteins, are high-molecular compounds containing nitrogen. The concept of "protein", first designated by Berzelius in 1838, comes from the Greek word and means "primary", which reflects the leading role of proteins in nature. The variety of proteins makes it possible for a huge number of living beings to exist: from bacteria to the human body. There are significantly more of them than other macromolecules, because proteins are the foundation of a living cell. They make up approximately 20% of the mass of the human body, more than 50% of the dry mass of the cell. This number of diverse proteins is explained by the properties of twenty different amino acids, which interact with each other and create polymer molecules.

An outstanding property of proteins is the ability to independently create a certain spatial structure characteristic of a particular protein. Proteins are biopolymers with peptide bonds. The chemical composition of proteins is characterized by a constant average nitrogen content of approximately 16%.

Life, as well as the growth and development of the body, are impossible without the function of protein amino acids to build new cells. Proteins cannot be replaced by other elements; their role in the human body is extremely important.

Functions of proteins

The need for proteins lies in the following functions:

• it is necessary for growth and development, as it is the main building material for the creation of new cells;
• controls metabolism, during which energy is released. After eating food, the metabolic rate increases, for example, if the food consists of carbohydrates, the metabolism accelerates by 4%, if it consists of proteins - by 30%;
• regulate in the body due to its hydrophilicity - the ability to attract water;
• strengthen the immune system by synthesizing antibodies that protect against infection and eliminate the threat of disease.

Products - sources of proteins

The human muscles and skeleton consist of living tissues that not only function but are also renewed throughout life. They recover from damage and retain their strength and durability. To do this, they require very specific nutrients. Food provides the body with the energy it needs for all processes, including muscle function, tissue growth and repair. And protein in the body is used both as a source of energy and as a building material.

Therefore, it is very important to observe its daily use in food. Protein-rich foods: chicken, turkey, lean ham, pork, beef, fish, shrimp, beans, lentils, bacon, eggs, nuts. All these products provide the body with protein and provide the energy necessary for life.

Lecture No. 1

TOPIC: "Amino acids".

Lecture outline:

1. Characteristics of amino acids

2. Peptides.

Characteristics of amino acids.

Amino acids are organic compounds, derivatives of hydrocarbons, the molecules of which include carboxyl and amino groups.

Proteins consist of amino acid residues connected by peptide bonds. To analyze the amino acid composition, protein hydrolysis is carried out followed by the isolation of amino acids. Let's consider the basic patterns characteristic of amino acids in proteins.

It has now been established that proteins contain a constantly occurring set of amino acids. There are 18 of them. In addition to those indicated, 2 more amino acid amides were discovered - asparagine and glutamine. They all got the name major(frequently occurring) amino acids. They are often figuratively called "magical" amino acids. In addition to major amino acids, there are also rare ones, those that are not often found in natural proteins. They are called minor.

Almost all protein amino acids belong to α – amino acids(the amino group is located at the first carbon atom after the carboxyl group). Based on the above, for most amino acids the general formula is valid:

N.H. 2 -CH-COOH

Where R are radicals with different structures.

Let's look at the formulas of protein amino acids, table. 2.

All α - amino acids, except aminoacetic (glycine), have an asymmetric α - carbon atom and exist in the form of two enantiomers. With rare exceptions, natural amino acids belong to the L series. Amino acids of the D genetic series were found only in the cell walls of bacteria and in antibiotics. The rotation angle is 20-30 0 degrees. Rotation can be right (7 amino acids) or left (10 amino acids).

H― *―NH 2 H 2 N―*―H

D - configuration L-configuration

(natural amino acids)

Depending on the predominance of amino or carboxyl groups, amino acids are divided into 3 subclasses:

Acidic amino acids. Carboxyl (acidic) groups predominate over amino groups (basic), for example, aspartic, glutamic acids.

Neutral amino acids The number of groups is equal. Glycine, alanine, etc.

Basic amino acids. Basic (amino groups) predominate over carboxyl (acidic) ones, for example, lysine.

In terms of physical and a number of chemical properties, amino acids differ sharply from the corresponding acids and bases. They dissolve better in water than in organic solvents; crystallize well; have high density and exceptionally high melting points. These properties indicate the interaction of amine and acid groups, as a result of which amino acids in the solid state and in solution (over a wide pH range) are in zwitterionic form (i.e., as internal salts). The mutual influence of groups is especially pronounced in α - amino acids, where both groups are in close proximity.

H 2 N - CH 2 COOH ↔ H 3 N + - CH 2 COO -

zwitterion

The zwitter ionic structure of amino acids is confirmed by their large dipole moment (at least 5010 -30 C  m), as well as the absorption band in the IR spectrum of a solid amino acid or its solution.

Amino acids are capable of entering into polycondensation reactions, leading to the formation of polypeptides of different lengths, which constitute the primary structure of the protein molecule.

H 2 N–CH(R 1)-COOH + H 2 N– CH(R 2) – COOH → H 2 N – CH(R 1) – CO-NH– CH(R 2) – COOH

Dipeptide

The C–N bond is called peptide communication

In addition to the 20 most common amino acids discussed above, some other amino acids have been isolated from hydrolysates of some specialized proteins. All of them are, as a rule, derivatives of ordinary amino acids, i.e. modified amino acids.

4-hydroxyproline , found in fibrillar protein collagen and some plant proteins; 5-oxylysine is found in collagen hydrolysates, desmozi n and isodesmosine isolated from hydrolysates of the fibrillar protein elastin. It appears that these amino acids are only found in this protein. Their structure is unusual: the 4th lysine molecules, connected by their R-groups, form a substituted pyridine ring. It is possible that due to this particular structure, these amino acids can form 4 radially diverging peptide chains. The result is that elastin, unlike other fibrillar proteins, is able to deform (stretch) in two mutually perpendicular directions. Etc.

From the listed protein amino acids, living organisms synthesize a huge number of diverse protein compounds. Many plants and bacteria can synthesize all the amino acids they need from simple inorganic compounds. In the body of humans and animals, approximately half of the amino acids are also synthesized. The other part of the amino acids can enter the human body only with dietary proteins.

- essential amino acids - are not synthesized in the human body, but are supplied only with food. Essential amino acids include 8 amino acids: valine, phenylalanine, isoleucine, leucine, lysine, methionine, threonine, tryptophan, phenylalanine.

- essential amino acids - can be synthesized in the human body from other components. Nonessential amino acids include 12 amino acids.

Both types of amino acids are equally important for humans: non-essential and essential. Most of the amino acids are used to build the body’s own proteins, but without essential amino acids the body cannot exist. Proteins, which contain essential amino acids, should make up about 16-20% of the adult diet (20-30g with a daily protein intake of 80-100g). In children's nutrition, the share of protein increases to 30% for schoolchildren, and to 40% for preschoolers. This is due to the fact that the child’s body is constantly growing and, therefore, needs a large amount of amino acids as plastic material for building proteins in muscles, blood vessels, the nervous system, skin and all other tissues and organs.

In these days of fast food and the general craze for fast food, the diet is often dominated by foods high in easily digestible carbohydrates and fats, and the share of protein foods is noticeably reduced. If there is a lack of any amino acids in the diet or during fasting in the human body for a short time, proteins of connective tissue, blood, liver and muscles can be destroyed, and the “building material” obtained from them - amino acids - is used to maintain the normal functioning of the most important organs - the heart and brain. The human body may experience a shortage of both essential and non-essential amino acids. Deficiency of amino acids, especially essential ones, leads to poor appetite, retarded growth and development, fatty liver and other severe disorders. The first “harbingers” of amino acid deficiency may be decreased appetite, deterioration of skin condition, hair loss, muscle weakness, fatigue, decreased immunity, and anemia. Such manifestations may occur in individuals who, in order to lose weight, follow a low-calorie, unbalanced diet with a sharp restriction of protein foods.

More often than others, vegetarians who deliberately avoid including complete animal protein in their diet face manifestations of a lack of amino acids, especially essential ones.

Excess amino acids are quite rare these days, but can cause the development of serious diseases, especially in children and adolescence. The most toxic are methionine (provokes the risk of heart attack and stroke), tyrosine (can provoke the development of arterial hypertension, lead to disruption of the thyroid gland) and histidine (can contribute to copper deficiency in the body and lead to the development of aortic aneurysm, joint diseases, early gray hair). , severe anemia). Under normal conditions of functioning of the body, when there is a sufficient amount of vitamins (B 6, B 12, folic acid) and antioxidants (vitamins A, E, C and selenium), excess amino acids are quickly converted into useful components and do not have time to “cause damage” to the body. An unbalanced diet causes a deficiency of vitamins and microelements, and an excess of amino acids can disrupt the functioning of systems and organs. This option is possible with long-term adherence to protein or low-carbohydrate diets, as well as with uncontrolled intake by athletes of protein-energy products (amino acid-vitamin cocktails) to increase weight and develop muscles.

Among the chemical methods, the most common method is amino acid score (scor - counting, counting). It is based on comparison of the amino acid composition of the protein of the product being evaluated with the amino acid composition standard (ideal) protein. After quantitative chemical determination of the content of each of the essential amino acids in the protein under study, the amino acid score (AS) for each of them is determined according to the formula

AC = (m ak . research / m ak . perfect ) 100

m ac. research - the content of essential amino acids (in mg) in 1 g of the protein being studied.

m ac. ideal - the content of essential amino acids (in mg) in 1 g of standard (ideal) protein.

Amino acid pattern FAO/WHO

Simultaneously with the determination of the amino acid score, limiting essential amino acid for a given protein , that is the one for which the speed is the smallest.

Peptides.

Two amino acids can be joined covalently by peptide connection with the formation of a dipeptide.

Three amino acids can be joined through two peptide bonds to form a tripeptide. A few amino acids form oligopeptides, and a large number of amino acids form polypeptides. Peptides contain only one α-amino group and one α-carboxyl group. These groups can be ionized at certain pH values. Like amino acids, they have characteristic titration curves and isoelectric points at which they do not move in an electric field.

Like other organic compounds, peptides participate in chemical reactions that are determined by the presence of functional groups: free amino group, free carboxy group and R-groups. Peptide bonds are susceptible to hydrolysis by a strong acid (for example, 6M HC1) or a strong base to form amino acids. Hydrolysis of peptide bonds is a necessary step in determining the amino acid composition of proteins. Peptide bonds can be broken by enzymes proteases.

Many naturally occurring peptides have biological activity at very low concentrations.

Peptides are potentially active pharmaceuticals, there are three ways receiving them:

1) isolation from organs and tissues;

2) genetic engineering;

3) direct chemical synthesis.

In the latter case, high demands are placed on the yield of products at all intermediate stages.

Amino acids are the structural chemical units or "building blocks" that make up proteins. Amino acids consist of 16% nitrogen, this is their main chemical difference from the other two essential nutrients - carbohydrates and fats. The importance of amino acids for the body is determined by the enormous role that proteins play in all life processes.

Every living organism, from the largest animals to tiny microbes, is made up of proteins. Various forms of proteins take part in all processes occurring in living organisms. In the human body, muscles, ligaments, tendons, all organs and glands, hair, and nails are formed from proteins. Proteins are found in fluids and bones. Enzymes and hormones that catalyze and regulate all processes in the body are also proteins. A deficiency of these nutrients in the body can lead to an imbalance in water balance, which causes swelling.

Each protein in the body is unique and exists for specific purposes. Proteins are not interchangeable. They are synthesized in the body from amino acids, which are formed as a result of the breakdown of proteins found in foods. Thus, it is amino acids, and not proteins themselves, that are the most valuable nutritional elements. In addition to the fact that amino acids form proteins that make up the tissues and organs of the human body, some of them act as neurotransmitters (neurotransmitters) or are their precursors.

Neurotransmitters are chemicals that transmit nerve impulses from one nerve cell to another. Thus, some amino acids are essential for normal brain function. Amino acids ensure that vitamins and minerals adequately perform their functions. Some amino acids directly provide energy to muscle tissue.

In the human body, many amino acids are synthesized in the liver. However, some of them cannot be synthesized in the body, so a person must obtain them from food. These essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Amino acids that are synthesized in the liver: alanine, arginine, asparagine, aspartic acid, citrulline, cysteine, gamma-aminobutyric acid, glutamine and glutamic acid, glycine, ornithine, proline, serine, taurine, tyrosine.

The process of protein synthesis occurs constantly in the body. If at least one essential amino acid is missing, protein formation stops. This can lead to a variety of serious problems, from poor digestion to depression and slow growth.

How does this situation arise? Easier than you might imagine. Many factors lead to this, even if your diet is balanced and you consume enough protein. Malabsorption in the gastrointestinal tract, infection, injury, stress, certain medications, the aging process and imbalances of other nutrients in the body can all lead to essential amino acid deficiencies.

Keep in mind that all of the above does not mean that consuming a lot of protein will solve any problems. In reality, it is not conducive to maintaining health.

Excess protein creates additional stress for the kidneys and liver, which need to process the products of protein metabolism, the main one being ammonia. It is very toxic to the body, so the liver immediately processes it into urea, which then travels through the bloodstream to the kidneys, where it is filtered and excreted.

As long as the amount of protein is not too high and the liver is functioning well, the ammonia is neutralized immediately and does not cause any harm. But if there is too much of it and the liver cannot cope with its neutralization (as a result of poor diet, digestive disorders and/or liver disease), toxic levels of ammonia are created in the blood. In this case, a lot of serious health problems can arise, including hepatic encephalopathy and coma.

Too high a concentration of urea also causes kidney damage and back pain. Therefore, it is not the quantity, but the quality of proteins consumed in food that is important. Currently, it is possible to obtain essential and non-essential amino acids in the form of biologically active food supplements.

This is especially important for various diseases and when using reduction diets. Vegetarians need supplements containing essential amino acids to ensure that the body receives everything it needs for normal protein synthesis.

There are different types of amino acid supplements available. Amino acids are part of some multivitamins and protein mixtures. There are commercially available formulas containing complexes of amino acids or containing one or two amino acids. They come in various forms: capsules, tablets, liquids and powders.

Most amino acids exist in two forms, the chemical structure of one being a mirror image of the other. These are called D- and L-forms, for example D-cystine and L-cystine.

D stands for dextra (right in Latin) and L stands for levo (left). These terms indicate the direction of rotation of the helix, which is the chemical structure of a given molecule. Proteins in animal and plant organisms are created mainly by L-forms of amino acids (with the exception of phenylalanine, which is represented by D, L forms).

Nutritional supplements containing L-amino acids are considered more suitable for the biochemical processes of the human body.
Free, or unbound, amino acids are the purest form. Therefore, when choosing an amino acid supplement, preference should be given to products containing L-crystalline amino acids standardized by the American Pharmacopoeia (USP). They do not require digestion and are absorbed directly into the bloodstream. After oral administration, they are absorbed very quickly and, as a rule, do not cause allergic reactions.

Individual amino acids are taken on an empty stomach, preferably in the morning or between meals with a small amount of vitamins B6 and C. If you are taking a complex of amino acids that includes all the essential ones, it is best to do this 30 minutes after or 30 minutes before meals. It is best to take both individual essential amino acids and a complex of amino acids, but at different times. Amino acids alone should not be taken for long periods of time, especially in high doses. It is recommended to take it for 2 months with a 2-month break.

Alanin

Alanine helps normalize glucose metabolism. A relationship has been established between excess alanine and infection with the Epstein-Barr virus, as well as chronic fatigue syndrome. One form of alanine, beta-alanine is a component of pantothenic acid and coenzyme A, one of the most important catalysts in the body.

Arginine

Arginine slows down the growth of tumors, including cancer, by stimulating the body's immune system. It increases the activity and size of the thymus gland, which produces T lymphocytes. In this regard, arginine is useful for people suffering from HIV infection and malignant neoplasms.

It is also used for liver diseases (cirrhosis and fatty degeneration), it promotes detoxification processes in the liver (primarily the neutralization of ammonia). Seminal fluid contains arginine, so it is sometimes used in the complex treatment of infertility in men. Connective tissue and skin also contain large amounts of arginine, so taking it is effective for various injuries. Arginine is an important component of metabolism in muscle tissue. It helps maintain optimal nitrogen balance in the body, as it participates in the transportation and neutralization of excess nitrogen in the body.

Arginine helps with weight loss because it causes a slight decrease in fat stores in the body.

Arginine is part of many enzymes and hormones. It has a stimulating effect on the production of insulin by the pancreas as a component of vasopressin (a pituitary hormone) and helps in the synthesis of growth hormone. Although arginine is synthesized in the body, its production may be reduced in newborns. Sources of arginine include chocolate, coconuts, dairy products, gelatin, meat, oats, peanuts, soybeans, walnuts, white flour, wheat and wheat germ.

People who have viral infections, including Herpes simplex, should not take arginine supplements and should avoid consuming foods rich in arginine. Pregnant and breastfeeding mothers should not take arginine supplements. Taking small doses of arginine is recommended for diseases of the joints and connective tissue, impaired glucose tolerance, liver diseases and injuries. Long-term use is not recommended.

Asparagine

Asparagine is necessary to maintain balance in the processes occurring in the central nervous system: it prevents both excessive excitation and excessive inhibition. It is involved in the processes of amino acid synthesis in the liver.

Since this amino acid increases vitality, a supplement based on it is used for fatigue. It also plays an important role in metabolic processes. Aspartic acid is often prescribed for diseases of the nervous system. It is useful for athletes, as well as for liver dysfunction. In addition, it stimulates the immune system by increasing the production of immunoglobulins and antibodies.

Aspartic acid is found in large quantities in plant proteins obtained from sprouted seeds and in meat products.

Carnitine

Strictly speaking, carnitine is not an amino acid, but its chemical structure is similar to that of amino acids, and therefore they are usually considered together. Carnitine is not involved in protein synthesis and is not a neurotransmitter. Its main function in the body is the transport of long-chain fatty acids, the oxidation of which releases energy. This is one of the main sources of energy for muscle tissue. Thus, carnitine increases the conversion of fat into energy and prevents the deposition of fat in the body, primarily in the heart, liver, and skeletal muscles.

Carnitine reduces the likelihood of developing diabetes complications associated with lipid metabolism disorders, slows down fatty liver degeneration in chronic alcoholism and the risk of heart disease. It has the ability to reduce triglyceride levels in the blood, promotes weight loss and increases muscle strength in patients with neuromuscular diseases and enhances the antioxidant effect of vitamins C and E.

Some variants of muscular dystrophy are believed to be associated with carnitine deficiency. With such diseases, people should receive more of this substance than is required according to the norms.

It can be synthesized in the body in the presence of iron, thiamine, pyridoxine and the amino acids lysine and methionine. Carnitine synthesis occurs in the presence of sufficient amounts of vitamin C. Insufficient amounts of any of these nutrients in the body leads to carnitine deficiency. Carnitine enters the body with food, primarily meat and other products of animal origin.

Most cases of carnitine deficiency are associated with a genetically determined defect in the process of its synthesis. Possible manifestations of carnitine deficiency include impaired consciousness, heart pain, muscle weakness, and obesity.

Men, due to their larger muscle mass, require more carnitine than women. Vegetarians are more likely to be deficient in this nutrient than non-vegetarians due to the fact that carnitine is not found in plant-based proteins.

Moreover, methionine and lysine (amino acids necessary for carnitine synthesis) are also not found in sufficient quantities in plant foods.

To get the required amount of carnitine, vegetarians should take supplements or eat lysine-fortified foods such as cornflakes.

Carnitine is presented in dietary supplements in various forms: in the form of D, L-carnitine, D-carnitine, L-carnitine, acetyl-L-carnitine.
It is preferable to take L-carnitine.

Citrulline

Citrulline is predominantly found in the liver. It increases energy supply, stimulates the immune system, and is converted into L-arginine during metabolism. It neutralizes ammonia, which damages liver cells.

Cysteine ​​and cystine

These two amino acids are closely related, each cystine molecule consists of two cysteine ​​molecules connected to each other. Cysteine ​​is very unstable and easily transforms into L-cystine, and thus one amino acid can easily change into another when needed.

Both amino acids are sulfur-containing amino acids and play an important role in the formation of skin tissue and are important for detoxification processes. Cysteine ​​is part of alpha keratin - the main protein of nails, skin and hair. It promotes collagen formation and improves skin elasticity and texture. Cysteine ​​is also found in other proteins in the body, including some digestive enzymes.

Cysteine ​​helps neutralize certain toxic substances and protects the body from the damaging effects of radiation. It is one of the most powerful antioxidants, and its antioxidant effect is enhanced when taken simultaneously with vitamin C and selenium.

Cysteine ​​is a precursor to glutathione, a substance that has a protective effect on liver and brain cells from damage by alcohol, certain medications and toxic substances contained in cigarette smoke. Cysteine ​​dissolves better than cystine and is utilized more quickly in the body, which is why it is often used in the complex treatment of various diseases. This amino acid is formed in the body from L-methionine, with the obligatory presence of vitamin B6.

Additional intake of cysteine ​​is necessary for rheumatoid arthritis, arterial diseases, and cancer. It accelerates recovery after operations, burns, binds heavy metals and soluble iron. This amino acid also accelerates fat burning and muscle tissue formation.

L-cysteine ​​has the ability to destroy mucus in the respiratory tract, which is why it is often used for bronchitis and emphysema. It accelerates healing processes in respiratory diseases and plays an important role in activating leukocytes and lymphocytes.

Since this substance increases the amount of glutathione in the lungs, kidneys, liver and red bone marrow, it slows down the aging process, for example, reducing the number of age spots. N-acetylcysteine ​​is more effective at increasing glutathione levels in the body than cystine or even glutathione itself.

People with diabetes should be careful when taking cysteine ​​supplements as it has the ability to inactivate insulin. If you have cystinuria, a rare genetic condition that leads to the formation of cystine stones, you should not take cysteine.

Dimethylglycine

Dimethylglycine is a derivative of glycine, the simplest amino acid. It is a constituent of many important substances, such as the amino acids methionine and choline, some hormones, neurotransmitters and DNA.

Dimethylglycine is found in small quantities in meat products, seeds and grains. Although there are no symptoms associated with dimethylglycine deficiency, taking dimethylglycine supplements has a number of benefits, including improved energy and mental performance.

Dimethylglycine also stimulates the immune system, reduces cholesterol and triglycerides in the blood, helps normalize blood pressure and glucose levels, and also helps normalize the function of many organs. It is also used for epileptic seizures.

Gamma-aminobutyric acid

Gamma-aminobutyric acid (GABA) functions as a neurotransmitter in the central nervous system in the body and is essential for metabolism in the brain. It is formed from another amino acid - glutamine. It reduces neuronal activity and prevents overexcitation of nerve cells.

Gamma-aminobutyric acid relieves anxiety and has a calming effect; it can also be taken as tranquilizers, but without the risk of addiction. This amino acid is used in the complex treatment of epilepsy and arterial hypertension. Since it has a relaxing effect, it is used in the treatment of sexual dysfunctions. In addition, GABA is prescribed for attention deficit disorder. Excess gamma-aminobutyric acid, however, can increase anxiety, causing shortness of breath and trembling of the limbs.

Glutamic acid

Glutamic acid is a neurotransmitter that transmits impulses in the central nervous system. This amino acid plays an important role in carbohydrate metabolism and promotes the penetration of calcium through the blood-brain barrier.

This amino acid can be used by brain cells as an energy source. It also neutralizes ammonia by removing nitrogen atoms in the process of forming another amino acid - glutamine. This process is the only way to neutralize ammonia in the brain.

Glutamic acid is used in the correction of behavioral disorders in children, as well as in the treatment of epilepsy, muscular dystrophy, ulcers, hypoglycemic conditions, complications of insulin therapy for diabetes mellitus and mental development disorders.

Glutamine

Glutamine is the amino acid most commonly found in free form in muscles. It very easily penetrates the blood-brain barrier and in brain cells passes into glutamic acid and vice versa, in addition, it increases the amount of gamma-aminobutyric acid, which is necessary to maintain normal brain function.

This amino acid also maintains normal acid-base balance in the body and a healthy gastrointestinal tract, and is necessary for the synthesis of DNA and RNA.

Glutamine is an active participant in nitrogen metabolism. Its molecule contains two nitrogen atoms and is formed from glutamic acid by adding one nitrogen atom. Thus, glutamine synthesis helps remove excess ammonia from tissues, primarily from the brain, and transport nitrogen within the body.

Glutamine is found in large quantities in muscles and is used to synthesize proteins in skeletal muscle cells. Therefore, nutritional supplements with glutamine are used by bodybuilders and in various diets, as well as to prevent muscle loss in diseases such as malignant neoplasms and AIDS, after operations and during long-term bed rest.

Additionally, glutamine is also used in the treatment of arthritis, autoimmune diseases, fibrosis, gastrointestinal diseases, peptic ulcers, and connective tissue diseases.

This amino acid improves brain activity and is therefore used for epilepsy, chronic fatigue syndrome, impotence, schizophrenia and senile dementia. L-glutamine reduces pathological cravings for alcohol, therefore it is used in the treatment of chronic alcoholism.

Glutamine is found in many foods of both plant and animal origin, but it is easily destroyed by heating. Spinach and parsley are good sources of glutamine, as long as they are consumed raw.

Dietary supplements containing glutamine should only be stored in a dry place, otherwise glutamine will convert into ammonia and pyroglutamic acid. Do not take glutamine if you have liver cirrhosis, kidney disease, or Reye's syndrome.

Glutathione

Glutathione, like carnitine, is not an amino acid. According to its chemical structure, it is a tripeptide obtained in the body from cysteine, glutamic acid and glycine.

Glutathione is an antioxidant. Most glutathione is found in the liver (some of it is released directly into the bloodstream), as well as in the lungs and gastrointestinal tract.

It is necessary for carbohydrate metabolism, and also slows down aging due to its effect on lipid metabolism and prevents the occurrence of atherosclerosis. Glutathione deficiency primarily affects the nervous system, causing problems with coordination, mental processes, and tremors.

The amount of glutathione in the body decreases with age. In this regard, older people should receive it additionally. However, it is preferable to use nutritional supplements containing cysteine, glutamic acid and glycine - that is, substances that synthesize glutathione. Taking N-acetylcysteine ​​is considered the most effective.

Glycine

Glycine slows down the degeneration of muscle tissue, as it is a source of creatine, a substance contained in muscle tissue and used in the synthesis of DNA and RNA. Glycine is necessary for the synthesis of nucleic acids, bile acids and non-essential amino acids in the body.

It is part of many antacid medications used for stomach diseases; it is useful for restoring damaged tissue, as it is found in large quantities in the skin and connective tissue.

This amino acid is necessary for the normal functioning of the central nervous system and the maintenance of good prostate health. It functions as an inhibitory neurotransmitter and thus can prevent epileptic seizures.

Glycine is used in the treatment of manic-depressive psychosis, and it can also be effective for hyperactivity. Excess glycine in the body causes a feeling of fatigue, but an adequate amount provides the body with energy. If necessary, glycine can be converted into serine in the body.

Histidine

Histidine is an essential amino acid that promotes tissue growth and repair, is part of the myelin sheaths that protect nerve cells, and is also necessary for the formation of red and white blood cells. Histidine protects the body from the damaging effects of radiation, helps remove heavy metals from the body and helps with AIDS.

Too high a histidine content can lead to stress and even mental disorders (agitation and psychosis).

Inadequate levels of histidine in the body worsen the condition of rheumatoid arthritis and deafness associated with damage to the auditory nerve. Methionine helps lower the level of histidine in the body.

Histamine, a very important component of many immunological reactions, is synthesized from histidine. It also promotes sexual arousal. In this regard, the simultaneous use of dietary supplements containing histidine, niacin and pyridoxine (necessary for the synthesis of histamine) may be effective for sexual disorders.

Since histamine stimulates the secretion of gastric juice, the use of histidine helps with digestive disorders associated with low acidity of gastric juice.

People suffering from manic depression should not take histidine unless a deficiency of this amino acid is clearly established. Histidine is found in rice, wheat and rye.

Isoleucine

Isoleucine is one of the BCAA amino acids and essential amino acids necessary for the synthesis of hemoglobin. It also stabilizes and regulates blood sugar levels and energy supply processes. Isoleucine metabolism occurs in muscle tissue.

Combined use with isoleucine and valine (BCAA) increases endurance and promotes muscle tissue recovery, which is especially important for athletes.

Isoleucine is necessary for many mental illnesses. A deficiency of this amino acid results in symptoms similar to hypoglycemia.

Food sources of isoleucine include almonds, cashews, chicken, chickpeas, eggs, fish, lentils, liver, meat, rye, most seeds, and soy proteins.

There are biologically active food supplements containing isoleucine. In this case, it is necessary to maintain the correct balance between isoleucine and two other branched BCAA amino acids - leucine and valine.

Leucine

Leucine is an essential amino acid, together with isoleucine and valine, one of the three branched BCAA amino acids. Acting together, they protect muscle tissue and are sources of energy, and also promote the restoration of bones, skin, and muscles, so their use is often recommended during the recovery period after injuries and operations.

Leucine also slightly lowers blood sugar levels and stimulates the release of growth hormone. Food sources of leucine include brown rice, beans, meat, nuts, soy flour and wheat flour.

Dietary supplements containing leucine are used in combination with valine and isoleucine. They should be taken with caution to avoid causing hypoglycemia. Excess leucine can increase the amount of ammonia in the body.

Lysine

Lysine is an essential amino acid that is part of almost any protein. It is necessary for normal bone formation and growth in children, promotes the absorption of calcium and maintains normal nitrogen metabolism in adults.

This amino acid is involved in the synthesis of antibodies, hormones, enzymes, collagen formation and tissue repair. Lysine is used during the recovery period after operations and sports injuries. It also lowers serum triglyceride levels.

Lysine has an antiviral effect, especially against viruses that cause herpes and acute respiratory infections. Taking supplements containing lysine in combination with vitamin C and bioflavonoids is recommended for viral diseases.

A deficiency of this essential amino acid can lead to anemia, hemorrhages in the eyeball, enzyme disorders, irritability, fatigue and weakness, poor appetite, slow growth and weight loss, as well as reproductive system disorders.

Food sources of lysine include cheese, eggs, fish, milk, potatoes, red meat, soy and yeast products.

Methionine

Methionine is an essential amino acid that helps process fats, preventing their deposition in the liver and on the walls of arteries. The synthesis of taurine and cysteine ​​depends on the amount of methionine in the body. This amino acid promotes digestion, provides detoxification processes (primarily the neutralization of toxic metals), reduces muscle weakness, protects against radiation exposure, and is useful for osteoporosis and chemical allergies.

This amino acid is used in complex therapy of rheumatoid arthritis and toxicosis of pregnancy. Methionine has a pronounced antioxidant effect, as it is a good source of sulfur, which inactivates free radicals. It is used for Gilbert's syndrome and liver dysfunction. Methionine is also necessary for the synthesis of nucleic acids, collagen and many other proteins. It is useful for women receiving oral hormonal contraceptives. Methionine lowers histamine levels in the body, which may be useful in schizophrenia when the amount of histamine is elevated.

Methionine in the body is converted into cysteine, which is a precursor to glutathione. This is very important in case of poisoning, when large amounts of glutathione are required to neutralize toxins and protect the liver.

Food sources of methionine: legumes, eggs, garlic, lentils, meat, onions, soybeans, seeds and yogurt.

Ornithine

Ornithine helps release growth hormone, which helps burn fat in the body. This effect is enhanced when ornithine is used in combination with arginine and carnitine. Ornithine is also essential for the immune system and liver function, participating in detoxification processes and the restoration of liver cells.

Ornithine in the body is synthesized from arginine and, in turn, serves as a precursor for citrulline, proline, and glutamic acid. High concentrations of ornithine are found in the skin and connective tissue, so this amino acid helps repair damaged tissue.

Dietary supplements containing ornithine should not be given to children, pregnant and nursing mothers, or to persons with a history of schizophrenia.

Phenylalanine

Phenylalanine is an essential amino acid. In the body, it can be converted into another amino acid - tyrosine, which, in turn, is used in the synthesis of two main neurotransmitters: dopamine and norepinephrine. Therefore, this amino acid affects mood, reduces pain, improves memory and learning ability, and suppresses appetite. It is used in the treatment of arthritis, depression, menstrual pain, migraines, obesity, Parkinson's disease and schizophrenia.

Phenylalanine is found in three forms: L-phenylalanine (the natural form and it is the one that is part of most proteins in the human body), D-phenylalanine (a synthetic mirror form, has an analgesic effect), DL-phenylalanine (combines the beneficial properties of the two previous forms, it is usually used for premenstrual syndrome.

Dietary supplements containing phenylalanine should not be given to pregnant women, persons with anxiety attacks, diabetes, high blood pressure, phenylketonuria, pigmented melanoma.

Proline

Proline improves skin condition by increasing collagen production and reducing its loss with age. Helps restore cartilaginous surfaces of joints, strengthens ligaments and heart muscle. To strengthen connective tissue, proline is best used in combination with vitamin C.

Proline enters the body mainly from meat products.

Serin

Serine is necessary for the normal metabolism of fats and fatty acids, the growth of muscle tissue and the maintenance of a normal immune system.

Serine is synthesized in the body from glycine. As a moisturizing agent, it is included in many cosmetic products and dermatological preparations.

Taurine

Taurine is found in high concentrations in the heart muscle, white blood cells, skeletal muscles, and the central nervous system. It is involved in the synthesis of many other amino acids, and is also a major component of bile, which is necessary for the digestion of fats, the absorption of fat-soluble vitamins and for maintaining normal blood cholesterol levels.

Therefore, taurine is useful for atherosclerosis, edema, heart disease, arterial hypertension and hypoglycemia. Taurine is necessary for the normal metabolism of sodium, potassium, calcium and magnesium. It prevents the removal of potassium from the heart muscle and therefore helps prevent certain heart rhythm disorders. Taurine has a protective effect on the brain, especially during dehydration. It is used in the treatment of anxiety and agitation, epilepsy, hyperactivity, and seizures.

Dietary supplements with taurine are given to children with Down syndrome and muscular dystrophy. In some clinics, this amino acid is included in complex therapy for breast cancer. Excessive excretion of taurine from the body occurs in various conditions and metabolic disorders.

Arrhythmias, disorders of platelet formation, candidiasis, physical or emotional stress, intestinal diseases, zinc deficiency and alcohol abuse lead to taurine deficiency in the body. Alcohol abuse also impairs the body's ability to absorb taurine.

In diabetes, the body's need for taurine increases, and vice versa, taking dietary supplements containing taurine and cystine reduces the need for insulin. Taurine is found in eggs, fish, meat, milk, but is not found in plant proteins.

It is synthesized in the liver from cysteine ​​and from methionine in other organs and tissues of the body, provided there is a sufficient amount of vitamin B6. In case of genetic or metabolic disorders that interfere with the synthesis of taurine, it is necessary to take a dietary supplement with this amino acid.

Threonine

Threonine is an essential amino acid that helps maintain normal protein metabolism in the body. It is important for the synthesis of collagen and elastin, helps the liver and is involved in fat metabolism in combination with aspartic acid and methionine.

Threonine is found in the heart, central nervous system, skeletal muscles and prevents the deposition of fats in the liver. This amino acid stimulates the immune system as it promotes the production of antibodies. Threonine is found in very small quantities in grains, so vegetarians are more likely to be deficient in this amino acid.

Tryptophan

Tryptophan is an essential amino acid required for the production of niacin. It is used to synthesize serotonin, one of the most important neurotransmitters, in the brain. Tryptophan is used for insomnia, depression and to stabilize mood.

It helps with hyperactivity disorder in children, is used for heart disease, to control body weight, reduce appetite, and also to increase the release of growth hormone. Helps with migraine attacks, helps reduce the harmful effects of nicotine. Deficiency of tryptophan and magnesium can increase spasms of the coronary arteries.

The richest food sources of tryptophan include brown rice, country cheese, meat, peanuts and soy protein.

Tyrosine

Tyrosine is a precursor to the neurotransmitters norepinephrine and dopamine. This amino acid is involved in mood regulation; a lack of tyrosine leads to a deficiency of norepinephrine, which in turn leads to depression. Tyrosine suppresses appetite, helps reduce fat storage, promotes melatonin production and improves adrenal, thyroid and pituitary function.

Tyrosine is also involved in phenylalanine metabolism. Thyroid hormones are formed when iodine atoms are added to tyrosine. It is therefore not surprising that low plasma tyrosine is associated with hypothyroidism.

Symptoms of tyrosine deficiency also include low blood pressure, low body temperature and restless leg syndrome.

Dietary supplements with tyrosine are used to relieve stress and are believed to help with chronic fatigue syndrome and narcolepsy. They are used for anxiety, depression, allergies and headaches, as well as for drug withdrawal. Tyrosine may be helpful in Parkinson's disease. Natural sources of tyrosine include almonds, avocados, bananas, dairy products, pumpkin seeds and sesame seeds.

Tyrosine can be synthesized from phenylalanine in the human body. Dietary supplements with phenylalanine are best taken before bed or with foods containing large amounts of carbohydrates.

During treatment with monoamine oxidase inhibitors (usually prescribed for depression), you should almost completely avoid foods containing tyrosine and not take dietary supplements with tyrosine, as this can lead to an unexpected and sharp rise in blood pressure.

Valin

Valine is an essential amino acid with a stimulating effect, one of the BCAA amino acids, and therefore can be used by muscles as an energy source. Valine is necessary for muscle metabolism, repair of damaged tissues and for maintaining normal nitrogen metabolism in the body.

Valine is often used to correct severe amino acid deficiencies resulting from drug addiction. Its excessively high level in the body can lead to symptoms such as paresthesia (pins and needles sensation) and even hallucinations.
Valine is found in the following foods: grains, meat, mushrooms, dairy products, peanuts, soy protein.

Valine supplementation should be balanced with the other branched chain amino acids BCAA L-leucine and L-isoleucine.

Proteins form the material basis of the chemical activity of the cell. The functions of proteins in nature are universal. Name proteins, the most accepted term in Russian literature corresponds to the term proteins(from Greek proteios- first). To date, great strides have been made in establishing the relationship between the structure and functions of proteins, the mechanism of their participation in the most important processes of the body's life, and in understanding the molecular basis of the pathogenesis of many diseases.

Depending on their molecular weight, peptides and proteins are distinguished. Peptides have a lower molecular weight than proteins. Peptides are more likely to have a regulatory function (hormones, enzyme inhibitors and activators, ion transporters across membranes, antibiotics, toxins, etc.).

12.1. α -Amino acids

12.1.1. Classification

Peptides and proteins are built from α-amino acid residues. The total number of naturally occurring amino acids exceeds 100, but some of them are found only in a certain community of organisms; the 20 most important α-amino acids are constantly found in all proteins (Scheme 12.1).

α-Amino acids are heterofunctional compounds whose molecules contain both an amino group and a carboxyl group at the same carbon atom.

Scheme 12.1.The most important α-amino acids*

* Abbreviations are used only to write amino acid residues in peptide and protein molecules. ** Essential amino acids.

The names of α-amino acids can be constructed using substitutive nomenclature, but their trivial names are more often used.

Trivial names for α-amino acids are usually associated with sources of isolation. Serine is part of silk fibroin (from lat. serieus- silky); Tyrosine was first isolated from cheese (from the Greek. tyros- cheese); glutamine - from cereal gluten (from German. Gluten- glue); aspartic acid - from asparagus sprouts (from lat. asparagus- asparagus).

Many α-amino acids are synthesized in the body. Some amino acids necessary for protein synthesis are not produced in the body and must come from outside. These amino acids are called irreplaceable(see diagram 12.1).

Essential α-amino acids include:

valine isoleucine methionine tryptophan

leucine lysine threonine phenylalanine

α-Amino acids are classified in several ways depending on the characteristic that serves as the basis for their division into groups.

One of the classification features is the chemical nature of the radical R. Based on this feature, amino acids are divided into aliphatic, aromatic and heterocyclic (see diagram 12.1).

Aliphaticα -amino acids. This is the largest group. Within it, amino acids are divided using additional classification features.

Depending on the number of carboxyl groups and amino groups in the molecule, the following are distinguished:

Neutral amino acids - one NH group each 2 and COOH;

Basic amino acids - two NH groups 2 and one group

COOH;

Acidic amino acids - one NH 2 group and two COOH groups.

It can be noted that in the group of aliphatic neutral amino acids the number of carbon atoms in the chain does not exceed six. At the same time, there are no amino acids with four carbon atoms in the chain, and amino acids with five and six carbon atoms have only a branched structure (valine, leucine, isoleucine).

An aliphatic radical may contain “additional” functional groups:

Hydroxyl - serine, threonine;

Carboxylic - aspartic and glutamic acids;

Thiol - cysteine;

Amide - asparagine, glutamine.

Aromaticα -amino acids. This group includes phenylalanine and tyrosine, constructed in such a way that the benzene rings in them are separated from the common α-amino acid fragment by the methylene group -CH 2-.

Heterocyclic α -amino acids. Histidine and tryptophan belonging to this group contain heterocycles - imidazole and indole, respectively. The structure and properties of these heterocycles are discussed below (see 13.3.1; 13.3.2). The general principle of constructing heterocyclic amino acids is the same as aromatic ones.

Heterocyclic and aromatic α-amino acids can be considered as β-substituted derivatives of alanine.

The amino acid also belongs to gerocyclic proline, in which the secondary amino group is included in the pyrrolidine

In the chemistry of α-amino acids, much attention is paid to the structure and properties of the “side” radicals R, which play an important role in the formation of the structure of proteins and the performance of their biological functions. Of great importance are such characteristics as the polarity of the “side” radicals, the presence of functional groups in the radicals and the ability of these functional groups to ionize.

Depending on the side radical, amino acids with non-polar(hydrophobic) radicals and amino acids c polar(hydrophilic) radicals.

The first group includes amino acids with aliphatic side radicals - alanine, valine, leucine, isoleucine, methionine - and aromatic side radicals - phenylalanine, tryptophan.

The second group includes amino acids that have polar functional groups in their radicals that are capable of ionization (ionogenic) or are unable to transform into an ionic state (nonionic) under body conditions. For example, in tyrosine the hydroxyl group is ionic (phenolic in nature), in serine it is nonionic (alcoholic in nature).

Polar amino acids with ionic groups in radicals under certain conditions can be in an ionic (anionic or cationic) state.

12.1.2. Stereoisomerism

The main type of construction of α-amino acids, i.e., the bond of the same carbon atom with two different functional groups, a radical and a hydrogen atom, in itself predetermines the chirality of the α-carbon atom. The exception is the simplest amino acid glycine H 2 NCH 2 COOH, which has no center of chirality.

The configuration of α-amino acids is determined by the configuration standard - glyceraldehyde. The location of the amino group in the standard Fischer projection formula on the left (similar to the OH group in l-glyceraldehyde) corresponds to the l-configuration, and on the right - to the d-configuration of the chiral carbon atom. By R, In the S-system, the α-carbon atom in all α-amino acids of the l-series has an S-configuration, and in the d-series, an R-configuration (the exception is cysteine, see 7.1.2).

Most α-amino acids contain one asymmetric carbon atom per molecule and exist as two optically active enantiomers and one optically inactive racemate. Almost all natural α-amino acids belong to the l-series.

The amino acids isoleucine, threonine and 4-hydroxyproline contain two chirality centers in the molecule.

Such amino acids can exist as four stereoisomers, representing two pairs of enantiomers, each of which forms a racemate. To build animal proteins, only one of the enantiomers is used.

The stereoisomerism of isoleucine is similar to the previously discussed stereoisomerism of threonine (see 7.1.3). Of the four stereoisomers, proteins contain l-isoleucine with the S configuration of both asymmetric carbon atoms C-α and C-β. The names of another pair of enantiomers that are diastereomers with respect to leucine use the prefix Hello-.

Cleavage of racemates. The source of α-amino acids of the l-series are proteins, which are subjected to hydrolytic cleavage for this purpose. Due to the great need for individual enantiomers (for the synthesis of proteins, medicinal substances, etc.) chemical methods for breaking down synthetic racemic amino acids. Preferred enzymatic method of digestion using enzymes. Currently, chromatography on chiral sorbents is used to separate racemic mixtures.

12.1.3. Acid-base properties

The amphotericity of amino acids is determined by acidic (COOH) and basic (NH 2) functional groups in their molecules. Amino acids form salts with both alkalis and acids.

In the crystalline state, α-amino acids exist as dipolar ions H3N+ - CHR-COO- (commonly used notation

The structure of the amino acid in non-ionized form is for convenience only).

In aqueous solution, amino acids exist in the form of an equilibrium mixture of dipolar ion, cationic and anionic forms.

The equilibrium position depends on the pH of the medium. For all amino acids, cationic forms predominate in strongly acidic (pH 1-2) and anionic forms in strongly alkaline (pH > 11) environments.

The ionic structure determines a number of specific properties of amino acids: high melting point (above 200? C), solubility in water and insolubility in non-polar organic solvents. The ability of most amino acids to dissolve well in water is an important factor in ensuring their biological functioning; the absorption of amino acids, their transport in the body, etc. are associated with it.

A fully protonated amino acid (cationic form), from the standpoint of Brønsted’s theory, is a dibasic acid,

By donating one proton, such a dibasic acid turns into a weak monobasic acid - a dipolar ion with one acid group NH 3 + . Deprotonation of the dipolar ion leads to the production of the anionic form of the amino acid - the carboxylate ion, which is a Brønsted base. The values ​​characterize

The basic acidic properties of the carboxyl group of amino acids usually range from 1 to 3; values pK a2 characterizing the acidity of the ammonium group - from 9 to 10 (Table 12.1).

Table 12.1.Acid-base properties of the most important α-amino acids

The equilibrium position, i.e., the ratio of different forms of an amino acid, in an aqueous solution at certain pH values ​​significantly depends on the structure of the radical, mainly on the presence of ionic groups in it, playing the role of additional acidic and basic centers.

The pH value at which the concentration of dipolar ions is maximum, and the minimum concentrations of cationic and anionic forms of an amino acid are equal, is calledisoelectric point (p/).

Neutralα -amino acids. These amino acids matterpIslightly lower than 7 (5.5-6.3) due to the greater ability to ionize the carboxyl group under the influence of the -/- effect of the NH 2 group. For example, alanine has an isoelectric point at pH 6.0.

Sourα -amino acids. These amino acids have an additional carboxyl group in the radical and are in a fully protonated form in a strongly acidic environment. Acidic amino acids are tribasic (according to Brøndsted) with three meaningspK a,as can be seen in the example of aspartic acid (p/ 3.0).

For acidic amino acids (aspartic and glutamic), the isoelectric point is at a pH much lower than 7 (see Table 12.1). In the body at physiological pH values ​​(for example, blood pH 7.3-7.5), these acids are in anionic form, since both carboxyl groups are ionized.

Basicα -amino acids. In the case of basic amino acids, the isoelectric points are located in the pH region above 7. In a strongly acidic environment, these compounds are also tribasic acids, the ionization stages of which are illustrated by the example of lysine (p/ 9.8).

In the body, basic amino acids are found in the form of cations, that is, both amino groups are protonated.

In general, no α-amino acid in vivois not at its isoelectric point and does not fall into a state corresponding to the lowest solubility in water. All amino acids in the body are in ionic form.

12.1.4. Analytically important reactions α -amino acids

α-Amino acids, as heterofunctional compounds, enter into reactions characteristic of both the carboxyl and amino groups. Some chemical properties of amino acids are due to the functional groups in the radical. This section discusses reactions that are of practical importance for the identification and analysis of amino acids.

Esterification.When amino acids react with alcohols in the presence of an acid catalyst (for example, hydrogen chloride gas), esters are obtained in the form of hydrochlorides in good yield. To isolate free esters, the reaction mixture is treated with ammonia gas.

Amino acid esters do not have a dipolar structure, therefore, unlike the parent acids, they dissolve in organic solvents and are volatile. Thus, glycine is a crystalline substance with a high melting point (292°C), and its methyl ester is a liquid with a boiling point of 130°C. Analysis of amino acid esters can be carried out using gas-liquid chromatography.

Reaction with formaldehyde. Of practical importance is the reaction with formaldehyde, which underlies the quantitative determination of amino acids by the method formol titration(Sørensen method).

The amphoteric nature of amino acids does not allow direct titration with alkali for analytical purposes. The interaction of amino acids with formaldehyde produces relatively stable amino alcohols (see 5.3) - N-hydroxymethyl derivatives, the free carboxyl group of which is then titrated with alkali.

Qualitative reactions. A feature of the chemistry of amino acids and proteins is the use of numerous qualitative (color) reactions, which previously formed the basis of chemical analysis. Nowadays, when research is carried out using physicochemical methods, many qualitative reactions continue to be used for the detection of α-amino acids, for example, in chromatographic analysis.

Chelation. With cations of heavy metals, α-amino acids as bifunctional compounds form intra-complex salts, for example, with freshly prepared copper(11) hydroxide under mild conditions, well-crystallizing chelates are obtained

blue copper(11) salts (one of the nonspecific methods for detecting α-amino acids).

Ninhydrin reaction. The general qualitative reaction of α-amino acids is the reaction with ninhydrin. The reaction product has a blue-violet color, which is used for visual detection of amino acids on chromatograms (on paper, in a thin layer), as well as for spectrophotometric determination on amino acid analyzers (the product absorbs light in the region of 550-570 nm).

Deamination. In laboratory conditions, this reaction is carried out by the action of nitrous acid on α-amino acids (see 4.3). In this case, the corresponding α-hydroxy acid is formed and nitrogen gas is released, the volume of which is used to determine the amount of amino acid that has reacted (Van-Slyke method).

Xanthoprotein reaction. This reaction is used to detect aromatic and heterocyclic amino acids - phenylalanine, tyrosine, histidine, tryptophan. For example, when concentrated nitric acid acts on tyrosine, a nitro derivative is formed, colored yellow. In an alkaline environment, the color becomes orange due to ionization of the phenolic hydroxyl group and an increase in the contribution of the anion to conjugation.

There are also a number of private reactions that allow the detection of individual amino acids.

Tryptophan detected by reaction with p-(dimethylamino)benzaldehyde in sulfuric acid by the appearance of a red-violet color (Ehrlich reaction). This reaction is used for the quantitative analysis of tryptophan in protein breakdown products.

Cysteine detected through several qualitative reactions based on the reactivity of the mercapto group it contains. For example, when a protein solution with lead acetate (CH3COO)2Pb is heated in an alkaline medium, a black precipitate of lead sulfide PbS is formed, which indicates the presence of cysteine ​​in proteins.

12.1.5. Biologically important chemical reactions

In the body, under the influence of various enzymes, a number of important chemical transformations of amino acids are carried out. Such transformations include transamination, decarboxylation, elimination, aldol cleavage, oxidative deamination, and oxidation of thiol groups.

Transamination is the main pathway for the biosynthesis of α-amino acids from α-oxoacids. The donor of the amino group is an amino acid present in cells in sufficient quantity or excess, and its acceptor is an α-oxoacid. In this case, the amino acid is converted into an oxoacid, and the oxoacid into an amino acid with the corresponding structure of radicals. As a result, transamination is a reversible process of interchange of amino and oxo groups. An example of such a reaction is the production of l-glutamic acid from 2-oxoglutaric acid. The donor amino acid can be, for example, l-aspartic acid.

α-Amino acids contain an electron-withdrawing amino group (more precisely, a protonated amino group NH) in the α-position to the carboxyl group 3 +), and therefore capable of decarboxylation.

Eliminationcharacteristic of amino acids in which the side radical in the β-position to the carboxyl group contains an electron-withdrawing functional group, for example, hydroxyl or thiol. Their elimination leads to intermediate reactive α-enamino acids, which easily transform into tautomeric imino acids (analogy with keto-enol tautomerism). As a result of hydration at the C=N bond and subsequent elimination of the ammonia molecule, α-imino acids are converted into α-oxo acids.

This type of transformation is called elimination-hydration. An example is the production of pyruvic acid from serine.

Aldol cleavage occurs in the case of α-amino acids, which contain a hydroxyl group in the β-position. For example, serine is broken down to form glycine and formaldehyde (the latter is not released in free form, but immediately binds to the coenzyme).

Oxidative deamination can be carried out with the participation of enzymes and the coenzyme NAD+ or NADP+ (see 14.3). α-Amino acids can be converted into α-oxoacids not only through transamination, but also through oxidative deamination. For example, α-oxoglutaric acid is formed from l-glutamic acid. At the first stage of the reaction, glutamic acid is dehydrogenated (oxidized) to α-iminoglutaric acid

acids. In the second stage, hydrolysis occurs, resulting in α-oxoglutaric acid and ammonia. The hydrolysis stage occurs without the participation of an enzyme.

The reaction of reductive amination of α-oxo acids occurs in the opposite direction. α-oxoglutaric acid, always contained in cells (as a product of carbohydrate metabolism), is converted in this way into L-glutamic acid.

Oxidation of thiol groups underlies the interconversions of cysteine ​​and cystine residues, providing a number of redox processes in the cell. Cysteine, like all thiols (see 4.1.2), is easily oxidized to form a disulfide, cystine. The disulfide bond in cystine is easily reduced to form cysteine.

Due to the ability of the thiol group to easily oxidize, cysteine ​​performs a protective function when the body is exposed to substances with high oxidative capacity. In addition, it was the first drug to show anti-radiation effects. Cysteine ​​is used in pharmaceutical practice as a stabilizer for drugs.

Conversion of cysteine ​​to cystine results in the formation of disulfide bonds, such as in reduced glutathione

(see 12.2.3).

12.2. Primary structure of peptides and proteins

Conventionally, it is believed that peptides contain up to 100 amino acid residues in a molecule (which corresponds to a molecular weight of up to 10 thousand), and proteins contain more than 100 amino acid residues (molecular weight from 10 thousand to several million).

In turn, in the group of peptides it is customary to distinguish oligopeptides(low molecular weight peptides) containing no more than 10 amino acid residues in the chain, and polypeptides, the chain of which includes up to 100 amino acid residues. Macromolecules with a number of amino acid residues approaching or slightly exceeding 100 do not distinguish between polypeptides and proteins; these terms are often used as synonyms.

A peptide and protein molecule can be formally represented as a product of polycondensation of α-amino acids, which occurs with the formation of a peptide (amide) bond between monomer units (Scheme 12.2).

The design of the polyamide chain is the same for the entire variety of peptides and proteins. This chain has an unbranched structure and consists of alternating peptide (amide) groups -CO-NH- and fragments -CH(R)-.

One end of the chain containing an amino acid with a free NH group 2, is called the N-terminus, the other is called the C-terminus,

Scheme 12.2.The principle of constructing a peptide chain

which contains an amino acid with a free COOH group. Peptide and protein chains are written from the N-terminus.

12.2.1. Structure of the peptide group

In the peptide (amide) group -CO-NH- the carbon atom is in a state of sp2 hybridization. The lone pair of electrons of the nitrogen atom enters into conjugation with the π-electrons of the C=O double bond. From the standpoint of electronic structure, the peptide group is a three-center p,π-conjugated system (see 2.3.1), the electron density in which is shifted towards the more electronegative oxygen atom. The C, O, and N atoms forming a conjugated system are located in the same plane. The electron density distribution in the amide group can be represented using the boundary structures (I) and (II) or the electron density shift as a result of the +M- and -M-effects of the NH and C=O groups, respectively (III).

As a result of conjugation, some alignment of bond lengths occurs. The C=O double bond is extended to 0.124 nm compared to the usual length of 0.121 nm, and the C-N bond becomes shorter - 0.132 nm compared to 0.147 nm in the usual case (Fig. 12.1). The planar conjugated system in the peptide group causes difficulty in rotation around the C-N bond (the rotation barrier is 63-84 kJ/mol). Thus, the electronic structure determines a fairly rigid flat structure of the peptide group.

As can be seen from Fig. 12.1, the α-carbon atoms of amino acid residues are located in the plane of the peptide group on opposite sides of the C-N bond, i.e., in a more favorable trans position: the side radicals R of amino acid residues in this case will be the most distant from each other in space.

The polypeptide chain has a surprisingly uniform structure and can be represented as a series of each other located at an angle.

Rice. 12.1.Planar arrangement of the peptide group -CO-NH- and α-carbon atoms of amino acid residues

to each other planes of peptide groups connected to each other through α-carbon atoms by Cα-N and Cα-Csp bonds 2 (Fig. 12.2). Rotation around these single bonds is very limited due to difficulties in the spatial placement of side radicals of amino acid residues. Thus, the electronic and spatial structure of the peptide group largely determines the structure of the polypeptide chain as a whole.

Rice. 12.2.The relative position of the planes of peptide groups in the polypeptide chain

12.2.2. Composition and amino acid sequence

With a uniformly constructed polyamide chain, the specificity of peptides and proteins is determined by two most important characteristics - amino acid composition and amino acid sequence.

The amino acid composition of peptides and proteins is the nature and quantitative ratio of their α-amino acids.

The amino acid composition is determined by analyzing peptide and protein hydrolysates, mainly by chromatographic methods. Currently, such analysis is carried out using amino acid analyzers.

Amide bonds are capable of hydrolysis in both acidic and alkaline environments (see 8.3.3). Peptides and proteins are hydrolyzed to form either shorter chains - this is the so-called partial hydrolysis, or a mixture of amino acids (in ionic form) - complete hydrolysis. Hydrolysis is usually carried out in an acidic environment, since many amino acids are unstable under alkaline hydrolysis conditions. It should be noted that the amide groups of asparagine and glutamine are also subject to hydrolysis.

The primary structure of peptides and proteins is the amino acid sequence, i.e. the order of alternation of α-amino acid residues.

The primary structure is determined by sequentially removing amino acids from either end of the chain and identifying them.

12.2.3. Structure and nomenclature of peptides

Peptide names are constructed by sequentially listing amino acid residues, starting from the N-terminus, with the addition of a suffix-il, except for the last C-terminal amino acid, for which its full name is retained. In other words, the names

amino acids that entered into the formation of a peptide bond due to “their” COOH group end in the name of the peptide with -il: alanil, valyl, etc. (for aspartic and glutamic acid residues the names “aspartyl” and “glutamyl” are used, respectively). The names and symbols of amino acids indicate their belonging to l -row, unless otherwise indicated ( d or dl).

Sometimes in the abbreviated notation the symbols H (as part of an amino group) and OH (as part of a carboxyl group) indicate the unsubstitution of the functional groups of terminal amino acids. This method is convenient for depicting functional derivatives of peptides; for example, the amide of the above peptide at the C-terminal amino acid is written H-Asn-Gly-Phe-NH2.

Peptides are found in all organisms. Unlike proteins, they have a more heterogeneous amino acid composition, in particular, they quite often include amino acids d -row. Structurally, they are also more diverse: they contain cyclic fragments, branched chains, etc.

One of the most common representatives of tripeptides is glutathione- found in the body of all animals, plants and bacteria.

Cysteine ​​in the composition of glutathione makes it possible for glutathione to exist in both reduced and oxidized forms.

Glutathione is involved in a number of redox processes. It functions as a protein protector, i.e., a substance that protects proteins with free SH thiol groups from oxidation with the formation of disulfide bonds -S-S-. This applies to those proteins for which such a process is undesirable. In these cases, glutathione takes on the action of an oxidizing agent and thus “protects” the protein. During the oxidation of glutathione, intermolecular cross-linking of two tripeptide fragments occurs due to a disulfide bond. The process is reversible.

12.3. Secondary structure of polypeptides and proteins

High molecular weight polypeptides and proteins, along with the primary structure, are also characterized by higher levels of organization, which are called secondary, tertiary And quaternary structures.

The secondary structure is described by the spatial orientation of the main polypeptide chain, the tertiary structure by the three-dimensional architecture of the entire protein molecule. Both secondary and tertiary structure are associated with the ordered arrangement of the macromolecular chain in space. The tertiary and quaternary structure of proteins is discussed in a biochemistry course.

It was shown by calculation that one of the most favorable conformations for a polypeptide chain is an arrangement in space in the form of a right-handed helix, called α-helix(Fig. 12.3, a).

The spatial arrangement of an α-helical polypeptide chain can be imagined by imagining that it wraps around a certain

Rice. 12.3.α-helical conformation of the polypeptide chain

cylinder (see Fig. 12.3, b). On average, there are 3.6 amino acid residues per turn of the helix, the pitch of the helix is ​​0.54 nm, and the diameter is 0.5 nm. The planes of two neighboring peptide groups are located at an angle of 108°, and the side radicals of amino acids are located on the outside of the helix, i.e., they are directed as if from the surface of the cylinder.

The main role in securing such a chain conformation is played by hydrogen bonds, which in the α-helix are formed between the carbonyl oxygen atom of each first and the hydrogen atom of the NH group of each fifth amino acid residue.

Hydrogen bonds are directed almost parallel to the axis of the α-helix. They keep the chain twisted.

Typically, protein chains are not completely helical, but only partially. Proteins such as myoglobin and hemoglobin contain fairly long α-helical regions, such as the myoglobin chain

75% spiralized. In many other proteins, the proportion of helical regions in the chain may be small.

Another type of secondary structure of polypeptides and proteins is β-structure, also called folded sheet, or folded layer. Elongated polypeptide chains are arranged in folded sheets, linked by many hydrogen bonds between the peptide groups of these chains (Fig. 12.4). Many proteins contain both α-helical and β-sheet structures.

Rice. 12.4.Secondary structure of the polypeptide chain in the form of a folded sheet (β-structure)