KETONIC ACIDS — organic matters, which molecular composition are carboxyl (COOH —) and carbonyl (— CO —), groups; serve as predecessors of many connections performing important biological functions in an organism. The essential disbolism taking place at a number of morbid conditions are followed by strengthening in a human body of these or those ketonic acids. At B1 hypovitaminosis in tissues of a brain collects Pyroracemic to - that what attach great value in a pathogeny of polyneurites to. At a disease of a diabetes mellitus (see. diabetes mellitus ) there are jumps carbohydrate and a lipometabolism, followed by emergence in blood and urine of ketoproducts — acetoacetic acid (see) and acetone (see).
Development of brain symptoms in patients with a liver failure (hepatic coma) is connected with disturbance of education and utilization alpha and keto-glutaric and oxalacetic to - t that involves braking of reactions of a cycle Tricarboxylic to - t and by that oxidizing exchange in tissues of a brain.
Disturbance of transformations of phenylalanine in an organism leads to accumulation in blood of a product of its deamination — phenyl-pyruvic to - you. At this disease known under the name of a phenyl-pyruvic oligophrenia (see. Fenilketonuriya ), at children heavy mental retardation is observed. The exception of food of children of phenylalanine promotes disappearance of the phenomena of toxicosis.
At people with defect of the gene coding synthesis of enzymes oxidizing decarboxylation of alpha ketonic acids with a branched chain of carbon atoms (see. Decarboxylation ), there is an accumulation alpha and ketoisovalerianic, alpha keto - beta methylvalerian and alpha and ketoisokapron to - t which are allocated with urine, giving it a specific smell of maple syrup, a so-called ketoaciduria. This state carries also the name of a leucinosis and is the reason of a heavy intellectual underdevelopment at children (see. Dekarboksilaznaya insufficiency ).
Depending on position of ketogroup in relation to a carboxyl distinguish alpha, beta and gamma ketonic acids (e.g., CH 3 COCOOH — Pyroracemic to - that, CH 3 COCH 2 COOH — acetoacetic to - that and CH 3 COCH 2 CH 2 COOH — levulinic to - that respectively). By the number of COOH-group To. share on monobasic (e.g., Pyroracemic to - that) and double-base (e.g., oxalacetic and alpha and keto-glutaric to - you). To. have chemical properties ketones (see) and acids (see. Acids and bases ).
Alpha Ketonic acids are formed in a live organism as intermediate substances in processes of biosynthesis and disintegration of alpha amino acids as a result of reactions of enzymatic interaminations (see) and oxidizing deaminations (see). In reactions of interamination of alpha ketonic acid act as acceptors of amino groups (NH 2 - groups) also create finally their general fund in the form of one amino acid, usually glutaminic, edges after reversible deamination turns into the ketoanalogue again — alpha and keto-glutaric to - that. At oxidizing deamination the majority of amino acids form the corresponding alpha ketonic acids which can be exposed to the return amination and inclusion in proteins or to catabolize to carbonic acid and water. It is known that alpha ketonic acids stimulate growth of live organisms almost in the same measure, as amino acids similar to them. Therefore in the conditions of deficit in food of amino acids existence in an organism of enough a-ketonic acids is important for creation of set of the amino acids necessary for biosynthesis of protein.
Through To. in an organism the constant interrelation between proteinaceous, carbohydrate and a lipometabolism is carried out. So, at disintegration glycogen (see) it is formed Pyroracemic to - that, edges after amination turns into alanine or after oxidizing decarboxylation — in atsetil-KOA, used for synthesis fatty acids (see), and also in other biosynthetic processes. Through education pyroracemic to - you in a cycle Tricarboxylic to - t (see. Tricarboxylic acids cycle ) or in lipometabolism (see) products of hydrolytic disintegration of proteins — alanine, cysteine, glycine, serine, threonine are involved. Pyroracemic to - that, asparagine and asparaginic to - that are sources of education oxalacetic to - you — necessary substrate of a cycle Tricarboxylic to - t, quantitative contents to-rogo in a cell affects the general speed of energy balance. In a cycle Tricarboxylic to - the t is formed alpha and keto-glutaric to - that, playing an important role in processes of a nitrogen metabolism. Through education alpha and keto-glutaric to - you energy balance joins arginine, a glutamine, glutaminic to - that, proline and a histidine. Alpha and Ketoisovalerianic, alpha keto - beta methylvalerian and alpha and ketoisokapron to - you are intermediate products of transformations of valine, an isoleucine and a leucine in amber to - that. Through education acetoacetic to - you and atsetil-KOA Exchange of phenylalanine, tyrosine and leucine is connected with a cycle Tricarboxylic to - t and a lipometabolism. Transformation of methionine in amber to - that goes through education alpha-oxobutyric to - you.
Identification To. in biol, material it is accompanied by difficulties owing to instability of many alpha ketonic acids. In the form of hydrazones of alpha ketonic acid are defined by a hromatografichesky method. At hydrogenation of hydrazones of alpha ketonic acids the corresponding amino acids which can be also identified hromatografichesk are formed. Quantitative definition of a-ketonic acids can be made by their decarboxylation with the participation of sulfate of caesium or hydrogen peroxide, and also by receiving bisulfite derivatives, on infrared and ultraviolet spectrums of absorption. For identification of some a-ketonic acids enzymatic methods can be used.
Bibliography Lenindzher A. Biochemistry, the lane with English, M., 1976; M e i s t e r A. Biochemistry of the amino acids, v. 1—2, N. Y., 1965; The metabolic basis inherited disease, ed. by J. B. Stanbury a. o., N. Y», 1972.
L. S. Haylova.