Amino acids react with water. Amino acids - nomenclature, preparation, chemical properties

Properties of amino acids can be divided into two groups: chemical and physical.

Chemical properties of amino acids

Depending on the compounds, amino acids can exhibit different properties.

Amino acid interactions:

Amino acids, as amphoteric compounds, form salts with both acids and alkalis.

As carboxylic acids, amino acids form functional derivatives: salts, esters, amides.

Interaction and properties of amino acids with reasons:
Salts are formed:

NH 2 -CH 2 -COOH + NaOH NH 2 -CH 2 -COONa + H2O

Sodium salt + 2-aminoacetic acid Sodium salt of aminoacetic acid (glycine) + water

Interaction with alcohols:

Amino acids can react with alcohols in the presence of hydrogen chloride gas, turning into ester. Esters amino acids do not have a bipolar structure and are volatile compounds.

NH 2 -CH 2 -COOH + CH 3 OH NH 2 -CH 2 -COOCH 3 + H 2 O.

Methyl ester / 2-aminoacetic acid /

Interaction with ammonia:

Amides are formed:

NH 2 -CH(R)-COOH + H-NH 2 = NH 2 -CH(R)-CONH 2 + H 2 O

Interaction of amino acids with strong acids:

We get salts:

HOOC-CH 2 -NH 2 + HCl → Cl (or HOOC-CH 2 -NH 2 *HCl)

These are the basic chemical properties of amino acids.

Physical properties of amino acids

Let's list physical properties amino acids:

• Colorless
• Have a crystalline form
• Most amino acids have a sweet taste, but depending on the radical (R), they can be bitter or tasteless
• Easily soluble in water, but poorly soluble in many organic solvents
• Amino acids have the property of optical activity
• Melts with decomposition at temperatures above 200°C
• Non-volatile
• Aqueous solutions of amino acids in acidic and alkaline environments conduct electric current

DEFINITION

Amino acids- these are complex organic compounds, which in their molecule simultaneously contain an amino group and a carboxyl group.

Amino acids are crystalline solids characterized by high temperatures melting and decomposing when heated. They dissolve well in water. These properties are explained by the possibility of the existence of amino acids in the form of internal salts (Fig. 1).

Rice. 1. Internal salt of aminoacetic acid.

Obtaining amino acids

The starting compounds for the production of amino acids are often carboxylic acids, into the molecule of which an amino group is introduced. For example, obtaining them from halogenated acids

CH 3 -C(Br)H-COOH + 2NH 3 →CH 3 -C(NH 2)H-COOH + NH 4 Br.

In addition, aldehydes (1), unsaturated acids (2) and nitro compounds (3) can serve as starting materials for the production of amino acids:

CH 3 -C(O)H + NH 3 + HCN → CH 3 -C(NH 2)H-C≡H + H 2 O;

CH 3 -C(NH 2)H-C≡H + H 2 O (H +) → CH 3 -C(NH 2)H-COOH + NH 3 (1).

CH 2 =CH-COOH + NH 3 → H 2 N-CH 2 -CH 2 -COOH (2);

O 2 N-C 6 H 4 -COOH + [H] →H 2 N-C 6 H 4 -COOH (3).

Chemical properties of amino acids

Amino acids as heterofunctional compounds enter into most reactions characteristic of carboxylic acids and amines. The presence of two different amino acids in molecules functional groups leads to the appearance of a number of specific properties.

Amino acids are amphoteric compounds. They react with both acids and bases:

NH 2 -CH 2 -COOH + HCl→ Cl

NH 2 -CH 2 -COOH + NaOH→ NH 2 -CH 2 -COONa + H 2 O

Aqueous solutions of amino acids have a neutral, alkaline and acidic environment depending on the number of functional groups. For example, glutamic acid forms an acidic solution, since it contains two carboxyl groups and one amino group, and lysine forms an alkaline solution, because it contains one carboxyl group and two amino groups.

Two amino acid molecules can interact with each other. In this case, a water molecule is split off and a product is formed in which fragments of the molecule are linked to each other by a peptide bond (-CO-NH-). For example:

The resulting compound is called a dipeptide. Substances made up of many amino acid residues are called polypeptides. Peptides are hydrolyzed by acids and bases.

Application of amino acids

Amino acids necessary for building the body are obtained by both humans and animals from food proteins.

γ-Aminobutyric acid is used medicinally (aminalone/gammalon) for mental illness; A whole range of nootropic drugs have been created on its basis, i.e. influencing thought processes.

ε-Aminocaproic acid is also used in medicine (hemostatic agent), and in addition it is a large-scale industrial product used to produce synthetic polyamide fiber - nylon.

Anthranilic acid is used for the synthesis of dyes, such as indigo blue, and is also involved in the biosynthesis of heterocyclic compounds.

Examples of problem solving

EXAMPLE 1

Exercise

Write the equations for the reactions of alanine with: a) sodium hydroxide; b) ammonium hydroxide; c) hydrochloric acid. Due to what groups does internal salt exhibit acidic and basic properties?

Answer

Amino acids are often depicted as compounds containing an amino group and a carboxyl group, but some of their physical and chemical properties are inconsistent with this structure. The structure of amino acids corresponds to a bipolar ion: H 3 N + -CH(R)-COO - . Let's write the formula of alanine as an internal salt: H 3 N + -CH(CH 3)-COO - . Based on this structural formula, we write the reaction equations: a) H 3 N + -CH(CH 3)-COO - + NaOH = H 2 N-CH(CH 3)-COONa + H 2 O; b) H 3 N + -CH(CH 3)-COO - + NH 3 ×H 2 O = H 2 N-CH(CH 3)-COONH 4 + H 2 O; c) H 3 N + -CH(CH 3) -COO - + HCl = Cl - . The internal salt of an amino acid reacts with bases as an acid, and with acids as a base. The acid group is N + H 3, the main group is COO -.

EXAMPLE 2

Exercise	When a solution of 9.63 g of an unknown monoaminocarboxylic acid was exposed to an excess of nitrous acid, 2.01 l of nitrogen was obtained at 748 mm. rt. Art. and 20 o C. Determine the molecular formula of this compound. Could this acid be one of the natural amino acids? If so, what kind of acid is it? The molecule of this acid does not contain a benzene ring.
Solution	Let's write the reaction equation: H 2 NC x H 2 x COOH + HONO = HO-C x H 2 x -COOH + N 2 + H 2 O. Let's find the amount of nitrogen substance at zero level using the Clapeyron-Mendeleev equation. To do this, we express temperature and pressure in SI units: T = 273 + 20 = 293 K; P = 101.325 × 748 / 760 = 99.7 kPa; n(N 2) = 99.7 × 2.01 / 8.31 × 293 = 0.082 mol. Using the reaction equation, we find the amount of amino acid substance and its molar mass. According to the equation n(H 2 NC x H 2 x COOH) = n(N 2) = 0.082 mol. M(H 2 NC x H 2 x COOH) = 9.63 / 0.082 = 117 g/mol. Let's define an amino acid. Let's create an equation and find x: 14x + 16 + 45 = 117; H2NC4H8COOH. Of the natural acids, valine may correspond to this composition.
Answer	This amino acid is valine.

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 tissues and organs human body, some of them act as neuromediators (neurotransmitters) or are their precursors.

Neurotransmitters are chemicals, transmitting 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. In the case when at least one essential amino acid is absent, the formation of proteins is suspended. 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, trauma, stress, taking certain medicines, 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 poor nutrition, 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 additives.

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.

Available different types supplements containing amino acids. Amino acids are part of some multivitamins and protein mixtures. There are commercially available formulas containing amino acid complexes 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. Animal proteins and plant organisms 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 the syndrome chronic fatigue. One form of alanine - beta-alanine is integral part 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 complex therapy 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 having viral infections, including Herpes simplex, should not take arginine in the form of dietary 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 not recommended.

Asparagine

Asparagine is necessary to maintain balance in the processes occurring in the central nervous system: 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 in large quantities found in proteins plant origin, 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 complications diabetes mellitus associated with disorders of fat metabolism, 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 must 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 quantity 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.

For men due to greater muscle mass requires 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 receive required quantity 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 quickly utilized in the body, so 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 break down mucus in respiratory tract, due to this, 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.

IN small quantities Dimethylglycine is found 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 state gastrointestinal tract, 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 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 health prostate gland. 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, promotes the removal of heavy metals from the body and helps with AIDS.

Too much histidine can lead to stress and even mental disorders(excitement 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 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 comply the right 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 is part of most proteins in the human body), D-phenylalanine (a synthetic mirror form, has an analgesic effect), DL-phenylalanine (combines beneficial properties 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, or 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 drugs.

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 part of the main component of bile, which is necessary for the digestion of fats, the absorption of fat-soluble vitamins and for the maintenance normal level cholesterol in the blood.

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 deposits, promotes melatonin production and improves adrenal function, thyroid gland and pituitary gland.

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

Symptoms of tyrosine deficiency also include decreased blood pressure, low body temperature and restless legs 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. It's excessive 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.

Amino acids exhibit properties of both acids and amines. So, they form salts (due to the acidic properties of the carboxyl group):

NH 2 CH 2 COOH + NaOH (NH 2 CH 2 COO)Na + H 2 O

glycine sodium glycinate

and esters (like other organic acids):

NH 2 CH 2 COOH + C 2 H 5 OHNH 2 CH 2 C(O)OC 2 H 5 + H 2 O

glycine ethylglycinate

With stronger acids, amino acids exhibit the properties of bases and form salts due to the basic properties of the amino group:

glycine wisteria chloride

The simplest protein is a polypeptide containing at least 70 amino acid residues in its structure and having a molecular weight of over 10,000 Da (dalton). Dalton - a unit of measurement for the mass of proteins, 1 dalton is equal to 1.66054·10 -27 kg (carbon mass unit). Similar compounds consisting of fewer amino acid residues are classified as peptides. Some hormones are peptides in nature - insulin, oxytocin, vasopressin. Some peptides are regulators of immunity. Some antibiotics (cyclosporin A, gramicidins A, B, C and S), alkaloids, toxins of bees and wasps, snakes, poisonous mushrooms (phalloidin and amanitin of the toadstool), cholera and botulinum toxins, etc. have a peptide nature.

Levels of structural organization of protein molecules.

The protein molecule has a complex structure. There are several levels of structural organization of a protein molecule - primary, secondary, tertiary and quaternary structures.

Primary structure is defined as a linear sequence of proteinogenic amino acid residues linked by peptide bonds (Fig. 5):

Fig.5. Primary structure of a protein molecule

The primary structure of a protein molecule is genetically determined for each specific protein in the nucleotide sequence of messenger RNA. The primary structure also determines higher levels of organization of protein molecules.

Secondary structure - conformation (i.e. location in space) of individual sections of the protein molecule. The secondary structure in proteins can be represented by an -helix, -structure (folded sheet structure) (Fig. 6).

Fig.6. Protein secondary structure

Protein secondary structure is maintained hydrogen bonds between peptide groups.

Tertiary structure - conformation of the entire protein molecule, i.e. spatial arrangement of the entire polypeptide chain, including the arrangement of side radicals. For a significant number of proteins, the coordinates of all protein atoms were obtained by X-ray diffraction analysis, with the exception of the coordinates of hydrogen atoms. All types of interactions take part in the formation and stabilization of the tertiary structure: hydrophobic, electrostatic (ionic), disulfide covalent bonds, hydrogen bonds. Radicals of amino acid residues participate in these interactions. Among the bonds holding the tertiary structure, it should be noted: a) disulfide bridge (- S - S -); b) ester bridge (between the carboxyl group and the hydroxyl group); c) salt bridge (between the carboxyl group and the amino group); d) hydrogen bonds.

In accordance with the shape of the protein molecule, determined by the tertiary structure, the following groups of proteins are distinguished:

1) Globular proteins , which have the shape of a globule (sphere). Such proteins include, for example, myoglobin, which has 5 α-helical segments and no β-folds, immunoglobulins, which do not have an α-helix; the main elements of the secondary structure are β-folds

2) Fibrillar proteins . These proteins have an elongated thread-like shape; they perform a structural function in the body. In the primary structure they have repeating regions and form a secondary structure that is fairly uniform for the entire polypeptide chain. Thus, protein α - keratin (the main protein component of nails, hair, skin) is built from extended α - helices. There are less common elements of secondary structure, for example, polypeptide chains of collagen, forming left-handed helices with parameters that differ sharply from the parameters of α-helices. In collagen fibers, three helical polypeptide chains are twisted into a single right-handed superhelix (Fig. 7):

Fig. 7 Tertiary structure of collagen

Quaternary structure of protein. The quaternary structure of proteins refers to the way in which individual polypeptide chains (identical or different) with a tertiary structure are arranged in space, leading to the formation of a structurally and functionally unified macromolecular formation (multimer). Not all proteins have a quaternary structure. An example of a protein with a quaternary structure is hemoglobin, which consists of 4 subunits. This protein is involved in the transport of gases in the body.

When breaking disulfide and weak types of bonds in molecules, all protein structures, except the primary one, are destroyed (completely or partially), and the protein loses its native properties (properties of a protein molecule inherent in it in its natural, natural (native) state). This process is called protein denaturation . Factors that cause protein denaturation include high temperatures, ultraviolet irradiation, concentrated acids and alkalis, salts of heavy metals and others.

Proteins are divided into simple (proteins), consisting only of amino acids, and complex (proteins), containing, in addition to amino acids, other non-protein substances, for example, carbohydrates, lipids, nucleic acids. The non-protein part of a complex protein is called a prosthetic group.

Simple proteins, consisting only of amino acid residues, are widespread in the animal and plant world. Currently, there is no clear classification of these compounds.

Histones

They have a relatively low molecular weight (12-13 thousand), with a predominance of alkaline properties. Localized mainly in cell nuclei, soluble in weak acids, precipitated by ammonia and alcohol. They have only tertiary structure. Under natural conditions, they are tightly bound to DNA and are part of nucleoproteins. The main function is the regulation of the transfer of genetic information from DNA and RNA (transmission can be blocked).

Protamines

These proteins have the lowest molecular weight (up to 12 thousand). Exhibits pronounced basic properties. Well soluble in water and weak acids. Contained in germ cells and make up the bulk of chromatin protein. Like histones, they form a complex with DNA and impart chemical stability to DNA, but unlike histones, they do not perform a regulatory function.

Glutelins

Plant proteins contained in gluten from the seeds of cereals and some other crops, in the green parts of plants. Insoluble in water, salt solutions and ethanol, but highly soluble in weak alkali solutions. They contain all essential amino acids and are complete food products.

Prolamins

Plant proteins. Contained in gluten of cereal plants. They are soluble only in 70% alcohol (this is explained by the high content of proline and non-polar amino acids in these proteins).

Proteinoids.

Proteinoids include proteins of supporting tissues (bone, cartilage, ligaments, tendons, nails, hair); they are characterized by a high sulfur content. These proteins are insoluble or poorly soluble in water, salt and water-alcohol mixtures. Proteinoids include keratin, collagen, fibroin.

Albumin

These are acidic proteins of low molecular weight (15-17 thousand), soluble in water and weak saline solutions. Precipitated by neutral salts at 100% saturation. They participate in maintaining the osmotic pressure of the blood and transport various substances with the blood. Contained in blood serum, milk, egg white.

Globulins

Molecular weight up to 100 thousand. Insoluble in water, but soluble in weak salt solutions and precipitate in less concentrated solutions (already at 50% saturation). Contained in plant seeds, especially legumes and oilseeds; in blood plasma and some other biological fluids. They perform the function of immune defense and ensure the body's resistance to viral infectious diseases.

Among nitrogen-containing organic matter there are connections with dual function. Particularly important of them are amino acids.

About 300 different amino acids are found in the cells and tissues of living organisms, but only 20 ( α-amino acids ) of them serve as units (monomers) from which peptides and proteins of all organisms are built (therefore they are called protein amino acids). The sequence of location of these amino acids in proteins is encoded in the nucleotide sequence of the corresponding genes. The remaining amino acids are found both in the form of free molecules and in bound form. Many of the amino acids are found only in certain organisms, and there are others that are found only in one of the great variety of described organisms. Most microorganisms and plants synthesize the amino acids they need; Animals and humans are not capable of producing the so-called essential amino acids obtained from food. Amino acids are involved in the metabolism of proteins and carbohydrates, in the formation of compounds important for organisms (for example, purine and pyrimidine bases, which are an integral part of nucleic acids), they are part of hormones, vitamins, alkaloids, pigments, toxins, antibiotics, etc.; Some amino acids serve as intermediaries in the transmission of nerve impulses.

Amino acids- organic amphoteric compounds, which include carboxyl groups - COOH and amino groups -NH 2 .

Amino acids can be considered as carboxylic acids, in the molecules of which the hydrogen atom in the radical is replaced by an amino group.

CLASSIFICATION

Amino acids are classified according to their structural characteristics.

1. Depending on the relative position of the amino and carboxyl groups, amino acids are divided into α-, β-, γ-, δ-, ε- etc.

2. Depending on the number of functional groups, acidic, neutral and basic groups are distinguished.

3. Based on the nature of the hydrocarbon radical, they distinguish aliphatic(fat), aromatic, sulfur-containing And heterocyclic amino acids. The amino acids listed above belong to the fatty series.

An example of an aromatic amino acid is para-aminobenzoic acid:

An example of a heterocyclic amino acid is tryptophan, an essential α-amino acid.

NOMENCLATURE

According to systematic nomenclature, the names of amino acids are formed from the names of the corresponding acids by adding the prefix amino and indicating the location of the amino group in relation to the carboxyl group. Numbering of the carbon chain from the carbon atom of the carboxyl group.

For example:

Another method of constructing the names of amino acids is also often used, according to which the prefix is ​​added to the trivial name of the carboxylic acid amino indicating the position of the amino group by a letter of the Greek alphabet.

Example:

For α-amino acidsR-CH(NH2)COOH

Which play an extremely important role in the life processes of animals and plants, trivial names are used.

Table.

Amino acid	Abbreviated designation	Structure of the radical (R)
Glycine	Gly	H-
Alanin	Ala (Ala)	CH 3 -
Valin	Val	(CH 3) 2 CH -
Leucine	Leu (Lei)	(CH 3) 2 CH – CH 2 -
Serin	Ser	OH-CH2-
Tyrosine	Tyr (Shooting Range)	HO – C 6 H 4 – CH 2 -
Aspartic acid	Asp (Asp)	HOOC – CH 2 -
Glutamic acid	Glu	HOOC – CH 2 – CH 2 -
Cysteine	Cys (Cis)	HS – CH 2 -
Asparagine	Asn (Asn)	O = C – CH 2 – │ NH 2
Lysine	Lys (Liz)	NH 2 – CH 2 - CH 2 – CH 2 -
Phenylalanine	Phen	C 6 H 5 – CH 2 -

If an amino acid molecule contains two amino groups, then the prefix is ​​used in its namediamino-, three NH 2 groups – triamino- etc.

Example:

The presence of two or three carboxyl groups is reflected in the name by the suffix –diovy or -triic acid:

ISOMERIA

1. Isomerism of the carbon skeleton

2. Isomerism of the position of functional groups

3. Optical isomerism

α-amino acids, except glycine NH 2 -CH 2 -COOH.

PHYSICAL PROPERTIES

Amino acids are crystalline substances with high (above 250°C) melting points, which differ little among individual amino acids and are therefore uncharacteristic. Melting is accompanied by decomposition of the substance. Amino acids are highly soluble in water and insoluble in organic solvents, which makes them similar to inorganic compounds. Many amino acids have a sweet taste.

RECEIVING

3. Microbiological synthesis. Microorganisms are known that during their life processes produce α - amino acids of proteins.

CHEMICAL PROPERTIES

Amino acids are amphoteric organic compounds; they are characterized by acid-base properties.

I . General properties

1. Intramolecular neutralization → a bipolar zwitterion is formed:

Aqueous solutions are electrically conductive. These properties are explained by the fact that amino acid molecules exist in the form of internal salts, which are formed by the transfer of a proton from the carboxyl to the amino group:

zwitterion

Aqueous solutions of amino acids are neutral, acidic or alkaline environment depending on the number of functional groups.

APPLICATION

1) amino acids are widely distributed in nature;

2) amino acid molecules are the building blocks from which all plant and animal proteins are built; amino acids necessary for building body proteins are obtained by humans and animals as part of food proteins;

3) amino acids are prescribed for severe exhaustion, after severe operations;

4) they are used to feed the sick;

5) amino acids are necessary as remedy for some diseases (for example, glutamic acid is used for nervous diseases, histidine for stomach ulcers);

6) some amino acids are used in agriculture for feeding animals, which has a positive effect on their growth;

7) have technical significance: aminocaproic and aminoenanthic acids form synthetic fibers - capron and enanth.

ABOUT THE ROLE OF AMINO ACIDS

Occurrence in nature and biological role of amino acids

Finding in nature and the biological role of amino acids