Amphoteric properties of amines. Amino acids
Amino acids exhibit the 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 ethyl glycinate
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 (daltons). 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 a smaller number of amino acid residues, are referred to as peptides. Peptides by their nature are some hormones - insulin, oxytocin, vasopressin. Some peptides are immune regulators. Some antibiotics (cyclosporin A, gramicidins A, B, C and S), alkaloids, toxins of bees and wasps, snakes, poisonous mushrooms (phalloidin and pale grebe amanitin), 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 a -helix, -structure (folded sheet structure) (Fig. 6).
Fig.6. Secondary structure of a protein
The secondary structure of a protein is supported by hydrogen bonds between peptide groups.
Tertiary structure - the conformation of the entire protein molecule, i.e. stacking in space of the entire polypeptide chain, including the stacking of side radicals. For a significant number of proteins, the coordinates of all protein atoms, except for the coordinates of hydrogen atoms, were obtained by X-ray diffraction analysis. All types of interactions take part in the formation and stabilization of the tertiary structure: hydrophobic, electrostatic (ionic), disulfide covalent bonds, hydrogen bonds. These interactions involve radicals of amino acid residues. Among the bonds holding the tertiary structure, it should be noted: a) disulfide bridge (- S - S -); b) ester bridge (between carboxyl group and hydroxyl group); c) salt bridge (between carboxyl group and amino group); d) hydrogen bonds.
In accordance with the shape of the protein molecule due to 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 that do not have an α-helix, the main elements of the secondary structure are β-folds
2) fibrillar proteins . These proteins have an elongated filamentous shape; they perform a structural function in the body. In the primary structure, they have repeating sections and form a fairly uniform secondary structure for the entire polypeptide chain. So, protein α - keratin (the main protein component of nails, hair, skin) is built from extended α - helices. There are less common elements of the secondary structure, for example, collagen polypeptide chains that form left-handed helices with parameters that differ sharply from those of α-helices. In collagen fibers, three helical polypeptide chains are twisted into a single right supercoil (Fig. 7):
Fig.7 Tertiary structure of collagen
Quaternary structure of the protein. Under the quaternary structure of proteins is meant a way of laying in space individual polypeptide chains (identical or different) with a tertiary structure, leading to the formation of a single macromolecular formation (multimer) in structural and functional respects. 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.
At break disulfide and weak types of bonds in molecules, all protein structures, except for the primary one, are destroyed (completely or partially), while the protein loses its native properties (properties of a protein molecule inherent in its natural, natural (native) state). This process is called protein denaturation . Factors that cause protein denaturation include high temperatures, ultraviolet radiation, concentrated acids and alkalis, salts of heavy metals, and others.
Proteins are classified 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 the prosthetic group.
Simple proteins, consisting only of amino acid residues, are widespread in the animal and plant kingdoms. 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 the nuclei of cells, soluble in weak acids, precipitated by ammonia and alcohol. They have only a tertiary structure. Under natural conditions, they are strongly associated with DNA and are part of nucleoproteins. The main function is the regulation of the transfer of genetic information from DNA and RNA (transmission blocking is possible).
Protamines
These proteins have the lowest molecular weight (up to 12 thousand). Shows the expressed basic properties. Highly soluble in water and weak acids. Contained in germ cells and make up the bulk of the chromatin protein. Like histones, they form a complex with DNA, give DNA chemical stability, but unlike histones, they do not perform a regulatory function.
Glutelins
Vegetable proteins contained in the gluten of seeds of cereals and some other crops, in the green parts of plants. Insoluble in water, salt and ethanol solutions, but highly soluble in weak alkali solutions. They contain all the essential amino acids and are a complete food.
Prolamins
vegetable proteins. Contained in the gluten of cereal plants. Soluble only in 70% alcohol (this is due to 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 hardly soluble in water, salt and water-alcohol mixtures. Proteinoids include keratin, collagen, fibroin.
Albumins
These are acidic proteins of low molecular weight (15-17 thousand), soluble in water and weak salt solutions. Precipitated by neutral salts at 100% saturation. Participate in maintaining the osmotic pressure of the blood, 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 precipitated in less concentrated solutions (already at 50% saturation). Contained in the seeds of plants, especially in legumes and oilseeds; in blood plasma and in some other biological fluids. They perform the function of immune protection, provide the body's resistance to viral infectious diseases.
1. Amino acids exhibit amphoteric properties and acids and amines, as well as specific properties due to the joint presence of these groups. In aqueous solutions, AMA exist in the form of internal salts (bipolar ions). Aqueous solutions of monoaminomonocarboxylic acids are neutral for litmus, because their molecules contain an equal number of -NH 2 - and -COOH groups. These groups interact with each other to form internal salts:
Such a molecule has opposite charges in two places: positive NH 3 + and negative on carboxyl –COO - . In this regard, the internal salt of AMA is called a bipolar ion or Zwitter-ion (Zwitter - hybrid).
A bipolar ion in an acidic environment behaves like a cation, since the dissociation of the carboxyl group is suppressed; in an alkaline environment - as an anion. There are pH values specific for each amino acid, in which the number of anionic forms in solution is equal to the number of cationic forms. The pH value at which the total charge of the AMA molecule is 0 is called the AMA isoelectric point (pI AA).
Aqueous solutions of monoaminodicarboxylic acids have an acid reaction of the environment:
HOOC-CH 2 -CH-COOH "- OOC-CH 2 -CH-COO - + H +
The isoelectric point of monoaminodicarboxylic acids is in an acidic environment and such AMA are called acidic.
Diaminomonocarboxylic acids have basic properties in aqueous solutions (participation of water in the dissociation process must be shown):
NH 2 -(CH 2) 4 -CH-COOH + H 2 O "NH 3 + -(CH 2) 4 -CH-COO - + OH -
The isoelectric point of diaminomonocarboxylic acids is at pH>7 and such AMA are called basic.
Being bipolar ions, amino acids exhibit amphoteric properties: they are able to form salts with both acids and bases:
Interaction with hydrochloric acid HCl leads to the formation of a salt:
R-CH-COOH + HCl ® R-CH-COOH
NH 2 NH 3 + Cl -
Reaction with a base leads to the formation of a salt:
R-CH (NH 2) -COOH + NaOH ® R-CH (NH 2) -COONa + H 2 O
2. Formation of complexes with metals- chelate complex. The structure of the copper salt of glycocol (glycine) can be represented by the following formula:
Almost all of the copper in the human body (100 mg) is bound to proteins (amino acids) in the form of these stable claw-shaped compounds.
3. Like other acids amino acids form esters, halogen anhydrides, amides.
4. Decarboxylation reactions occur in the body with the participation of special decarboxylase enzymes: the resulting amines (tryptamine, histamine, serotinin) are called biogenic amines and are regulators of a number of physiological functions of the human body.
5. Interaction with formaldehyde(aldehydes)
R-CH-COOH + H 2 C \u003d O ® R-CH-COOH
Formaldehyde binds the NH 2 - group, the -COOH group remains free and can be titrated with alkali. Therefore, this reaction is used for the quantitative determination of amino acids (Sorensen method).
6. Interaction with nitrous acid leads to the formation of hydroxy acids and the release of nitrogen. The volume of released nitrogen N 2 determine its quantitative content in the object under study. This reaction is used for the quantitative determination of amino acids (Van Slyke method):
R-CH-COOH + HNO 2 ® R-CH-COOH + N 2 + H 2 O
This is one way of deamination of AMK outside the body.
7. Acylation of amino acids. The amino group of AMA can be acylated with acid chlorides and anhydrides already at room temperature.
The product of the recorded reaction is acetyl-α-aminopropionic acid.
Acyl derivatives of AMA are widely used in the study of their sequence in proteins and in the synthesis of peptides (protection of the amino group).
8.specific properties, reactions associated with the presence and mutual influence of amino and carboxyl groups - the formation of peptides. A common property of a-AMA is polycondensation process leading to the formation of peptides. As a result of this reaction, amide bonds are formed at the site of interaction between the carboxyl group of one AMA and the amino group of another AMA. In other words, peptides are amides formed as a result of the interaction of amino groups and amino acid carboxyls. The amide bond in such compounds is called a peptide bond (disassemble the structure of the peptide group and the peptide bond: a three-center p, p-conjugated system)
Depending on the number of amino acid residues in a molecule, di-, tri-, tetrapeptides, etc. are distinguished. up to polypeptides (up to 100 AMK residues). Oligopeptides contain from 2 to 10 AMK residues, proteins - more than 100 AMK residues. In general, a polypeptide chain can be represented by the scheme:
H 2 N-CH-CO-NH-CH-CO-NH-CH-CO-... -NH-CH-COOH
Where R 1 , R 2 , ... R n are amino acid radicals.
The concept of proteins.
The most important biopolymers of amino acids are proteins - proteins. There are about 5 million in the human body. various proteins that are part of the skin, muscles, blood and other tissues. Proteins (proteins) got their name from the Greek word "protos" - the first, most important. Proteins perform a number of important functions in the body: 1. Building function; 2. Transport function; 3. Protective function; 4. Catalytic function; 5. Hormonal function; 6. Nutritional function.
All natural proteins are formed from amino acid monomers. During the hydrolysis of proteins, a mixture of AMA is formed. There are 20 of these AMKs.
4. Illustrative material: presentation
5. Literature:
Main literature:
1. Bioorganic chemistry: textbook. Tyukavkina N.A., Baukov Yu.I. 2014
- Seitembetov T.S. Chemistry: textbook - Almaty: TOO "EVERO", 2010. - 284 p.
- Bolysbekova S. M. Chemistry of biogenic elements: textbook - Semey, 2012. - 219 p. : silt
- Verentsova L.G. Inorganic, physical and colloidal chemistry: textbook - Almaty: Evero, 2009. - 214 p. : ill.
- Physical and colloidal chemistry / Under the editorship of A.P. Belyaev .- M .: GEOTAR MEDIA, 2008
- Verentseva L.G. Inorganic, physical and colloidal chemistry, (verification tests) 2009
Additional literature:
- Ravich-Shcherbo M.I., Novikov V.V. Physical and colloidal chemistry. M. 2003.
2. Slesarev V.I. Chemistry. Fundamentals of the chemistry of the living. St. Petersburg: Himizdat, 2001
3. Ershov Yu.A. General chemistry. Biophysical chemistry. Chemistry of biogenic elements. M.: VSh, 2003.
4. Asanbayeva R.D., Iliyasova M.I. Theoretical foundations of the structure and reactivity of biologically important organic compounds. Almaty, 2003.
- Guide to laboratory studies in bioorganic chemistry, ed. ON THE. Tyukavkina. M., Bustard, 2003.
- Glinka N.L. General chemistry. M., 2003.
- Ponomarev V.D. Analytical chemistry part 1,2 2003
6. Control questions (feedback):
1. What determines the structure of the polypeptide chain as a whole?
2. What does protein denaturation lead to?
3. What is called the isoelectric point?
4. What amino acids are called essential?
5. How are proteins formed in our body?
Similar information.
Amino acids contain amino and carboxyl groups and exhibit all the properties characteristic of compounds with such functional groups. When writing amino acid reactions, formulas with non-ionized amino and carboxy groups are used.
1) reactions on the amino group. The amino group in amino acids exhibits the usual properties of amines: amines are bases, and in reactions they act as nucleophiles.
1. Reaction of amino acids as bases. When an amino acid reacts with acids, ammonium salts are formed:
glycine hydrochloride, glycine hydrochloride salt
2. Action of nitrous acid. Under the action of nitrous acid, hydroxy acids are formed and nitrogen and water are released:
This reaction is used to quantify free amine groups in amino acids as well as in proteins.
3. Formation of N - acyl derivatives, acylation reaction.
Amino acids react with anhydrides and acid halides, forming N - acyl derivatives of amino acids:
Benzyl ether sodium salt N carbobenzoxyglycine - chloroformic glycine
Acylation is one way to protect the amino group. N-acyl derivatives are of great importance in the synthesis of peptides, since N-acyl derivatives are easily hydrolyzed to form a free amino group.
4. Formation of Schiff bases. When a - amino acids interact with aldehydes, substituted imines (Schiff bases) are formed through the stage of formation of carbinolamines:
alanine formaldehyde N-methylol derivative of alanine
5. Alkylation reaction. The amino group in a-amino acid is alkylated to form N-alkyl derivatives:
The reaction with 2,4-dinitrofluorobenzene is of the greatest importance. The resulting dinitrophenyl derivatives (DNP derivatives) are used in determining the amino acid sequence in peptides and proteins. The interaction of a-amino acids with 2,4-dinitrofluorobenzene is an example of a nucleophilic substitution reaction in the benzene ring. Due to the presence of two strong electron-withdrawing groups in the benzene ring, the halogen becomes mobile and enters into a substitution reaction:
2,4 - dinitro -
fluorobenzene N - 2,4 - dinitrophenyl - a - amino acid
(DNFB) DNF - derivatives of a - amino acids
6. Reaction with phenylisothiocyanate. This reaction is widely used in determining the structure of peptides. Phenylisothiocyanate is a derivative of isothiocyanic acid H-N=C=S. The interaction of a - amino acids with phenylisothiocyanate proceeds according to the mechanism of the reaction of nucleophilic addition. In the resulting product, an intramolecular substitution reaction is further carried out, leading to the formation of a cyclic substituted amide: phenylthiohydantoin.
Cyclic compounds are obtained in quantitative yield and are phenyl derivatives of thiohydantoin (FTH - derivatives) - amino acids. FTG - derivatives differ in the structure of the radical R.
In addition to the usual salts, a-amino acids can form intra-complex salts with heavy metal cations under certain conditions. For all a - amino acids, beautifully crystallizing, intensely blue-colored intra-complex (chelate) copper salts are very characteristic):
Alanine ethyl ester
The formation of esters is one of the methods for protecting the carboxyl group in the synthesis of peptides.
3. Formation of acid halides. When a-amino acids with a protected amino group are treated with sulfur oxydichloride (thionyl chloride) or phosphorus oxide-trichloride (phosphorus oxychloride), acid chlorides are formed:
Obtaining acid halides is one of the ways to activate the carboxyl group in peptide synthesis.
4. Obtaining anhydrides a - amino acids. Acid halides have a very high reactivity, which reduces the selectivity of the reaction when they are used. Therefore, a more frequently used method for activating the carboxyl group in peptide synthesis is its transformation into an anhydride group. Anhydrides are less active than acid halides. When an a-amino acid having a protected amino group interacts with ethyl chloroformate (ethyl chloroformate), an anhydride bond is formed:
5. Decarboxylation. a - Amino acids having two electron-withdrawing groups on the same carbon atom are easily decarboxylated. Under laboratory conditions, this is carried out by heating amino acids with barium hydroxide. This reaction occurs in the body with the participation of decarboxylase enzymes with the formation of biogenic amines:
ninhydrin
The ratio of amino acids to heat. When a-amino acids are heated, cyclic amides are formed, called diketopiperazines:
Diketopiperazine
g - and d - Amino acids easily split off water and cyclize to form internal amides, lactams:
g - lactam (butyrolactam)
In cases where the amino and carboxyl groups are separated by five or more carbon atoms, when heated, polycondensation occurs with the formation of polymeric polyamide chains with the elimination of a water molecule.
Amino acids are the structural chemical units or "building blocks" that make up proteins. Amino acids are 16% nitrogen, which is their main chemical difference from the other two most important nutrients - carbohydrates and fats. The importance of amino acids for the body is determined by the huge 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 are involved in all processes occurring in living organisms. In the human body, proteins form muscles, ligaments, tendons, all organs and glands, hair, nails. Proteins are part of the 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 water imbalance, 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 the amino acids, and not the proteins themselves, that are the most valuable elements of nutrition. In addition to the fact that amino acids form proteins that are part of 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 the normal functioning of the brain. Amino acids contribute to the fact that vitamins and minerals adequately perform their functions. Some amino acids provide energy directly 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 get them with 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 is ongoing in the body. In the case when at least one essential amino acid is missing, the formation of proteins stops. This can lead to a wide variety of serious problems - from indigestion to depression and stunted growth.
How does such a 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, certain medications, the aging process, and other nutrient imbalances in the body can all lead to essential amino acid deficiencies.
It should be borne in mind that all of the above does not mean that eating a large amount of protein will help solve any problems. In fact, it does not contribute to the preservation of 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 enters 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 working well, ammonia is neutralized immediately and does no harm. But if there is too much of it and the liver cannot cope with its neutralization (as a result of malnutrition, indigestion and / or liver disease), a toxic level of ammonia is created in the blood. In this case, a lot of serious health problems can arise, up to hepatic encephalopathy and coma.
Too high a concentration of urea also causes kidney damage and back pain. Therefore, it is not the quantity that is important, but the quality of proteins consumed with food. Currently, it is possible to obtain essential and non-essential amino acids in the form of biologically active food supplements.
This is especially important in various diseases and when using reduction diets. Vegetarians need such supplements containing essential amino acids so that the body receives everything necessary for normal protein synthesis.
There are different types of amino acid supplements. Amino acids are part of some multivitamins, protein mixtures. There are commercially available formulas containing complexes of amino acids or containing one or two amino acids. They are presented 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. They are called D- and L-forms, such as D-cystine and L-cystine.
D means dextra (right in Latin), and L means levo (respectively, left). These terms denote the direction of rotation of the helix, which is the chemical structure of a given molecule. Proteins of 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).
Food supplements containing L-amino acids are considered to be 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 as standardized by the American Pharmacopoeia (USP). They do not need to be digested 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, best in the morning or between meals with a small amount of vitamins B6 and C. If you are taking an amino acid complex that includes all essential amino acids, this is best done 30 minutes after or 30 minutes before a meal. It is best to take both individual essential amino acids and a complex of amino acids, but at different times. Separate amino acids should not be taken for a long time, especially in high doses. Recommend reception within 2 months with a 2-month break.
Alanine
Alanine contributes to the normalization of glucose metabolism. A relationship has been established between an excess of alanine and infection with the Epstein-Barr virus, as well as chronic fatigue syndrome. One form of alanine, beta-alanine, is a constituent 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, 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 treatment of infertility in men. There is also a large amount of arginine in the connective tissue and skin, so its use is effective for various injuries. Arginine is an important metabolic component in muscle tissue. It helps to maintain an optimal nitrogen balance in the body, as it is involved in the transportation and neutralization of excess nitrogen in the body.
Arginine helps to reduce weight, as it causes some reduction in body fat stores.
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 (pituitary hormone) and helps the synthesis of growth hormone. Although arginine is synthesized in the body, its production may be reduced in newborns. Sources of arginine are chocolate, coconuts, dairy products, gelatin, meat, oats, peanuts, soybeans, walnuts, white flour, wheat, and wheat germ.
People with viral infections, including Herpes simplex, should not take arginine supplements and should avoid arginine-rich foods. Pregnant and breastfeeding mothers should not take arginine supplements. Taking small doses of arginine is recommended for diseases of the joints and connective tissue, for 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 synthesis of amino acids in the liver.
Since this amino acid enhances vitality, supplementation 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 violations of liver function. 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 germinated 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, in the process of oxidation of which energy is released. It 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 complications of diabetes mellitus associated with disorders of fat metabolism, slows down fatty degeneration of the liver in chronic alcoholism and the risk of heart disease. It has the ability to reduce blood triglyceride levels, promote weight loss and increase muscle strength in patients with neuromuscular diseases, and enhance the antioxidant effect of vitamins C and E.
Some variants of muscular dystrophies are believed to be associated with carnitine deficiency. With such diseases, people should receive more of this substance than is required by the norms.
It can be synthesized in the body in the presence of iron, thiamine, pyridoxine, and the amino acids lysine and methionine. The synthesis of carnitine is carried out in the presence of also a sufficient amount of vitamin C. An insufficient amount of any of these nutrients in the body leads to a deficiency of carnitine. Carnitine enters the body with food, primarily with meat and other animal products.
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 greater muscle mass, require more carnitine than women. Vegetarians are more likely to be deficient in this nutrient than non-vegetarians because carnitine is not found in plant proteins.
Moreover, methionine and lysine (amino acids necessary for the synthesis of carnitine) are also not found in plant foods in sufficient quantities.
Vegetarians should take supplements or eat lysine-fortified foods such as corn flakes to get the carnitine they need.
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 in the process of metabolism turns into L-arginine. It neutralizes ammonia, which damages liver cells.
cysteine and cystine
These two amino acids are closely related to each other, each cystine molecule consists of two cysteine molecules connected to each other. Cysteine is very unstable and readily converts to L-cystine, and thus one amino acid is readily converted to another when needed.
Both amino acids are sulfur-containing and play an important role in the formation of skin tissues, 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 a component of other body proteins, including some digestive enzymes.
Cysteine helps to neutralize some 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 with vitamin C and selenium.
Cysteine is a precursor to glutathione, a substance that protects liver and brain cells from damage from alcohol, certain drugs, and toxic substances found in cigarette smoke. Cysteine dissolves better than cystine, and is more quickly utilized in the body, so it is more 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 disease, and cancer. It accelerates recovery after operations, burns, binds heavy metals and soluble iron. This amino acid also accelerates the burning of fat and the formation of muscle tissue.
L-cysteine has the ability to break down mucus in the airways, which is why it is often used for bronchitis and emphysema. It accelerates the healing process in respiratory diseases and plays an important role in the activation of 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, by reducing the number of age spots. N-acetylcysteine is more effective at raising 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 causes cystine stones, you should not take cysteine.
Dimethylglycine
Dimethylglycine is a derivative of glycine, the simplest amino acid. It is a component of many important substances, such as the amino acids methionine and choline, some hormones, neurotransmitters and DNA.
Dimethylglycine is found in small amounts in meat products, seeds, and grains. Although no symptoms are associated with dimethylglycine deficiency, dimethylglycine supplementation has a number of beneficial effects, 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 contributes to the normalization of the function of many organs. It is also used for epileptic seizures.
Gamma aminobutyric acid
Gamma-aminobutyric acid (GABA) acts as a neurotransmitter of the central nervous system in the body and is indispensable for metabolism in the brain. It is formed from another amino acid - glutamine. It reduces the activity of neurons and prevents overexcitation of nerve cells.
Gamma-aminobutyric acid relieves arousal and has a calming effect, it can be taken in the same way 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 dysfunction. In addition, GABA is prescribed for attention deficit disorder. An excess of gamma-aminobutyric acid, however, can increase anxiety, cause 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 the brain cells passes into glutamic acid and vice versa, in addition, it increases the amount of gamma-aminobutyric acid, which is necessary to maintain the normal functioning of the brain.
This amino acid also maintains a normal acid-base balance in the body and a healthy state of the 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, the synthesis of glutamine helps to 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, glutamine supplements are used by bodybuilders and in various diets, as well as to prevent muscle loss in diseases such as malignancy and AIDS, after surgery and during prolonged bed rest.
Additionally, glutamine is also used in the treatment of arthritis, autoimmune diseases, fibrosis, diseases of the gastrointestinal tract, peptic ulcers, 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 craving for alcohol, therefore it is used in the treatment of chronic alcoholism.
Glutamine is found in many foods, both plant and animal, but is easily destroyed by heat. Spinach and parsley are good sources of glutamine, provided they are consumed raw.
Food supplements containing glutamine should only be stored in a dry place, otherwise glutamine will be converted to ammonia and pyroglutamic acid. Do not take glutamine for cirrhosis of the liver, kidney disease, Reye's syndrome.
Glutathione
Glutathione, like carnitine, is not an amino acid. According to the 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 the effect on lipid metabolism and prevents the occurrence of atherosclerosis. Glutathione deficiency affects primarily the nervous system, causing impaired coordination, thought 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. The most effective is the intake of N-acetylcysteine.
Glycine
Glycine slows down the degeneration of muscle tissue, as it is a source of creatine, a substance found in muscle tissue and used in the synthesis of DNA and RNA. Glycine is essential for the synthesis of nucleic acids, bile acids, and non-essential amino acids in the body.
It is part of many antacid preparations used for diseases of the stomach, it is useful for repairing damaged tissues, as it is found in large quantities in the skin and connective tissue.
This amino acid is essential for the normal functioning of the central nervous system and the maintenance of good prostate health. It acts as an inhibitory neurotransmitter and thus may prevent epileptic seizures.
Glycine is used in the treatment of manic-depressive psychosis, it can also be effective in hyperactivity. An excess of glycine in the body causes a feeling of fatigue, but an adequate amount provides the body with energy. If necessary, glycine in the body can be converted to serine.
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 required 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 high a histidine content can lead to stress and even mental disorders (arousal and psychosis).
Inadequate levels of histidine in the body worsen rheumatoid arthritis and deafness associated with damage to the auditory nerve. Methionine helps to 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 intake of dietary supplements containing histidine, niacin and pyridoxine (necessary for the synthesis of histamine) may be effective in 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 depressive illness should not take histidine unless a deficiency of this amino acid has been clearly established. Histidine is found in rice, wheat and rye.
Isoleucine
Isoleucine is one of the BCAAs and essential amino acids required for the synthesis of hemoglobin. It also stabilizes and regulates blood sugar levels and energy supply processes. Isoleucine metabolism occurs in muscle tissue.
Combined with isoleucine and valine (BCAA) increases endurance and promotes muscle tissue recovery, which is especially important for athletes.
Isoleucine is essential for many mental illnesses. Deficiency of this amino acid leads to symptoms similar to hypoglycemia.
Dietary sources of isoleucine include almonds, cashews, chicken meat, chickpeas, eggs, fish, lentils, liver, meat, rye, most seeds, soy proteins.
There are biologically active food supplements containing isoleucine. In this case, it is necessary to maintain the correct balance between isoleucine and the other two branched-chain amino acids BCAA - leucine and valine.
Leucine
Leucine is an essential amino acid, together with isoleucine and valine, one of the three branched-chain amino acids BCAA. Acting together, they protect muscle tissue and are sources of energy, and also contribute to the restoration of bones, skin, muscles, so their use is often recommended during the recovery period after injuries and operations.
Leucine also somewhat lowers blood sugar levels and stimulates the release of growth hormone. Dietary sources of leucine include brown rice, beans, meat, nuts, soy and wheat flour.
Biologically active food supplements containing leucine are used in combination with valine and isoleucine. They should be taken with caution so as not to cause hypoglycemia. Excess leucine can increase the amount of ammonia in the body.
Lysine
Lysine is an essential amino acid found in almost all proteins. It is necessary for normal bone formation and growth in children, promotes calcium absorption 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 in 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. Supplementation containing lysine in combination with vitamin C and bioflavonoids is recommended for viral diseases.
Deficiency of this essential amino acid can lead to anemia, bleeding 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 are cheese, eggs, fish, milk, potatoes, red meat, soy and yeast products.
Methionine
Methionine is an essential amino acid that helps to 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 the complex therapy of rheumatoid arthritis and toxemia 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, liver dysfunction. Methionine is also required for the synthesis of nucleic acids, collagen and many other proteins. It is useful for women taking oral hormonal contraceptives. Methionine lowers the level of histamine in the body, which can be useful in schizophrenia when the amount of histamine is elevated.
Methionine in the body is converted to cysteine, which is the precursor of glutathione. This is very important in case of poisoning, when a large amount of glutathione is required to neutralize toxins and protect the liver.
Food sources of methionine: legumes, eggs, garlic, lentils, meat, onions, soybeans, seeds, and yogurt.
Ornithine
Ornithine aids in the release of growth hormone, which promotes fat burning in the body. This effect is enhanced by the use of ornithine in combination with arginine and carnitine. Ornithine is also necessary for the immune system and liver function, participating in detoxification processes and restoration of liver cells.
Ornithine in the body is synthesized from arginine and, in turn, serves as a precursor for citrulline, proline, glutamic acid. High concentrations of ornithine are found in the skin and connective tissue, so this amino acid helps repair damaged tissues.
Dietary supplements containing ornithine should not be given to children, pregnant or nursing mothers, or persons with a history of schizophrenia.
Phenylalanine
Phenylalanine is an essential amino acid. In the body, it can turn 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, period pain, migraine, obesity, Parkinson's disease and schizophrenia.
Phenylalanine occurs in three forms: L-phenylalanine (the natural form and it 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.
Biologically active food supplements containing phenylalanine are not given to pregnant women, people with anxiety attacks, diabetes, high blood pressure, phenylketonuria, pigmentary melanoma.
Proline
Proline improves skin condition by increasing collagen production and reducing its loss with age. Helps in the restoration of the cartilaginous surfaces of the joints, strengthens the ligaments and the heart muscle. To strengthen the connective tissue, proline is best used in combination with vitamin C.
Proline enters the body mainly from meat products.
Serene
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 part of the main component of bile, which is necessary for the digestion of fats, the absorption of fat-soluble vitamins, and to maintain normal blood cholesterol levels.
Therefore, taurine is useful in atherosclerosis, edema, heart disease, arterial hypertension and hypoglycemia. Taurine is essential for the normal metabolism of sodium, potassium, calcium and magnesium. It prevents the excretion of potassium from the heart muscle and therefore helps prevent certain heart rhythm disorders. Taurine has a protective effect on the brain, especially when dehydrated. It is used in the treatment of anxiety and agitation, epilepsy, hyperactivity, seizures.
Dietary supplements with taurine are given to children with Down syndrome and muscular dystrophy. In some clinics, this amino acid is included in the complex therapy of 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, bowel disease, zinc deficiency and alcohol abuse lead to a deficiency of taurine in the body. Alcohol abuse also disrupts 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. With genetic or metabolic disorders that interfere with the synthesis of taurine, it is necessary to take dietary supplements with this amino acid.
Threonine
Threonine is an essential amino acid that contributes to the maintenance of normal protein metabolism in the body. It is important for the synthesis of collagen and elastin, helps the liver and is involved in the metabolism of fats in combination with aspartic acid and methionine.
Threonine is found in the heart, central nervous system, skeletal muscles and prevents the deposition of fat in the liver. This amino acid stimulates the immune system, as it promotes the production of antibodies. Threonine is found in very small amounts 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 in the brain, one of the most important neurotransmitters. Tryptophan is used for insomnia, depression and to stabilize mood.
It helps with hyperactivity syndrome 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 to reduce the harmful effects of nicotine. Tryptophan and magnesium deficiency can exacerbate coronary artery spasms.
The richest dietary 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 to reduce fat deposits, promotes the production of melatonin and improves the functions of the adrenal glands, thyroid gland and pituitary gland.
Tyrosine is also involved in the metabolism of phenylalanine. Thyroid hormones are formed by the addition of iodine atoms to tyrosine. Therefore, it is not surprising that low plasma tyrosine is associated with hypothyroidism.
Other symptoms of tyrosine deficiency include low blood pressure, low body temperature, and restless leg syndrome.
Dietary supplements with tyrosine are used to relieve stress and are thought 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 useful in Parkinson's disease. Natural sources of tyrosine are almonds, avocados, bananas, dairy products, pumpkin seeds, and sesame seeds.
Tyrosine can be synthesized from phenylalanine in the human body. Phenylalanine supplements are best taken at bedtime or with foods high in carbohydrates.
Against the background of treatment with monoamine oxidase inhibitors (usually prescribed for depression), you should almost completely abandon products containing tyrosine and do not take dietary supplements with tyrosine, as this can lead to an unexpected and sharp rise in blood pressure.
Valine
Valine is an essential amino acid that has a stimulating effect, one of the BCAA amino acids, so it can be used by muscles as an energy source. Valine is essential 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 levels in the body can lead to symptoms such as paresthesia (goosebumps) up to hallucinations.
Valine is found in the following foods: cereals, meat, mushrooms, dairy products, peanuts, soy protein.
Supplementation of valine should be balanced with other BCAAs, L-leucine and L-isoleucine.
The chemical behavior of amino acids is determined by two functional groups -NH 2 and -COOH. Amino acids are characterized by reactions at the amino group, the carboxyl group and at the radical part, while, depending on the reagent, the interaction of substances can go through one or more reaction centers.
Amphoteric nature of amino acids. Having both an acidic and a basic group in the molecule, amino acids in aqueous solutions behave like typical amphoteric compounds. In acidic solutions, they exhibit basic properties, reacting as bases, in alkaline solutions, as acids, forming two groups of salts, respectively:
Due to their amphotericity in a living organism, amino acids play the role of buffer substances that maintain a certain concentration of hydrogen ions. Buffer solutions obtained by the interaction of amino acids with strong bases are widely used in bioorganic and chemical practice. Salts of amino acids with mineral acids are more soluble in water than free amino acids. Salts with organic acids are sparingly soluble in water and are used for the identification and separation of amino acids.
Reactions due to the amino group. With the participation of the amino group, amino acids form ammonium salts with acids, are acylated, alkylated , react with nitrous acid and aldehydes according to the following scheme:
Alkylation is carried out with the participation of R-Ha1 or Ar-Hal:
Acid chlorides or acid anhydrides (acetyl chloride, acetic anhydride, benzyloxycarbonyl chloride) are used in the acylation reaction:
Acylation and alkylation reactions are used to protect the NH 2 group of amino acids in the process of peptide synthesis.
Reactions due to the carboxyl group. With the participation of the carboxyl group, amino acids form salts, esters, amides, acid chlorides in accordance with the scheme below:
If at the -carbon atom in the hydrocarbon radical there is an electron-withdrawing substituent (NO 2, CC1 3, COOH, COR, etc.), which polarizes the CCOOH bond, then carboxylic acids easily undergo decarboxylation reactions. Decarboxylation of -amino acids containing + NH 3 group as a substituent leads to the formation of biogenic amines. In a living organism, this process proceeds under the action of the enzyme decarboxylase and vitamin pyridoxal phosphate.
Under laboratory conditions, the reaction is carried out by heating -amino acids in the presence of CO 2 absorbers, for example, Ba(OH) 2 .
Decarboxylation of -phenyl--alanine, lysine, serine, and histidine yields phenamine, 1,5-diaminopentane (cadaverine), 2-aminoethanol-1 (colamine), and tryptamine, respectively.
Reactions of amino acids with the participation of a side group. When the amino acid tyrosine is nitrated with nitric acid, an orange-colored dinitro derivative is formed (xantoprotein test):
Redox transitions take place in the cysteine-cystine system:
2 HS CH 2 CH(NH 2)COOH HOOCCH(NH 2)CH 2 S–S CH 2 CH(NH 2)COOH
HOOCCH(NH2)CH2 S– S CH 2 CH(NH 2)COOH 2 HS CH 2 CH(NH 2)COOH
In some reactions, amino acids react on both functional groups at the same time.
Formation of complexes with metals. Almost all -amino acids form complexes with divalent metal ions. The most stable are the complex internal copper salts (chelate compounds), which are formed as a result of interaction with copper (II) hydroxide and are colored blue:
The action of nitrous acid for aliphatic amino acids leads to the formation of hydroxy acids, aromatic - diazo compounds.
Formation of hydroxy acids:
Diazotization reaction:
with the release of molecular nitrogen N 2:
2. without the release of molecular nitrogen N 2:
The chromophore group of azobenzene -N=N in azo compounds causes yellow, yellow, orange or other color of substances when absorbed in the visible light region (400-800 nm). Auxochromic group
COOH changes and enhances the color due to π, π - conjugation with the π - electronic system of the main group of the chromophore.
The ratio of amino acids to heat. When heated, amino acids decompose to form various products, depending on their type. When heated -amino acids as a result of intermolecular dehydration, cyclic amides are formed - diketopiperazines :
valine (Val) diisopropyl derivative
diketopiperazine
When heated -amino acids ammonia is split off from them with the formation of α, β-unsaturated acids with a conjugated system of double bonds:
β-aminovaleric acid pentenoic acid
(3-aminopentanoic acid)
Heating - And -amino acids accompanied by intramolecular dehydration and the formation of internal cyclic amides – lactams:
γ-aminoisovaleric acid lactam γ-aminoisovaleric
(4-amino-3-methylbutanoic acid) acids