Biochemistry

A prerequisite for transamination is the participation of dicarboxylic amino acids (glutamic and aspartic), which in the form of their corresponding ketoacids - a-ketoglutaric and oxaloacetic acid can interact with all amino acids, with the exception of lysine, threonine and arginine. When transamination occurs, the amino group is directly transferred from amino acid to keto acid, and keto groupsfrom keto acid to amino acid without the release of ammonia. This process proceeds in several stages. In general, the reaction looks like this: a-Glutamic acid Pyruvic acid COOH 1 + CH 3 I z~x COOH + CHj 1 (CH 2 ) 2 < ----- — (CH 2 ) 2 c-^Hj ch -^ h J) 1 COOH 1 COOH COOH COOH a-Ketoglutaiic acid Alanine The reaction is catalyzed by enzymes belonging to the class of transferases, their prosthetic group is phosphorpiridoxal - phosphorus ester of vitamin Вб. The transamination process is widespread in wildlife. Its feature is easy reversibility. Transamination reactions play a large role in metabolism. The most important processes depend on them, such as the biosynthesis of many dispensable amino acids from the corresponding ketoacids, the breakdown of amino acids, the combination of carbohydrate and amino acid metabolism pathways, the alanine amino acid can form from the glucose breakdown products, for example pyruvic acid, and vice versa. Decarboxylation of amino acids A decarboxylation process is catalyzed by decarboxylases specific for each amino acid, a pyridoxal phosphate of which is a prosthetic group. These enzymes belong to the lyases class. The decarboxylation process, which consists in the removal of CO 2 from amino acids with the formation of amines, can be shown in the following scheme: 167