Biochemistry

specific proteins (albumin, globulin, fibrinogen, etc.), the remaining amino acids are carried by blood flow to all organs and tissues, transported inside the cells, where they are used for biosynthesis of proteins instead of destroyed ones . Unused amino acids are oxidized to the final metabolic products. The process of rotting tissue proteins is catalyzed by tissue enzymes - cathepsin proteinases. The ratio between the amino acids in decaying and synthesized proteins is different, so some of the free amino acids must be converted to other amino acids or oxidized to simple compounds and removed from the body. Therefore, the body has an intracellular supply of amino acids, which is largely replenished due to the processes of interconversion of amino acids, hydrolysis of proteins, synthesis of amino acids and their entry from extracellular fluid. At the same time, due to the synthesis of proteins and other reactions (the formation of urea, purines, etc.), free amino acids are constantly removed from the extracellular fluid. Amino acid metabolism Various types of amino acid metabolism are based on three types of reactions: on the amine and carboxyl groups and on the side chain. Reactions on the amine group include deamination, transamination, reductive amination, and on the carboxyl group, decarboxylation. A nitrogen-free part of the carbon skeleton of amino acids undergoes various transformations with the formation of compounds, which can be included in the Krebs cycle for further oxidation. Ways of the intracellular transformation of amino acids are complex and intersect with many other metabolic reactions, as a result of which intermediate products of amino acid metabolism can serve as a necessary precursor for the synthesis of various components of the cell and are biologically active substances. The catabolism of amino acids in mammals occurs mainly in the liver and weaker in the kidneys. Amino acid deamination The essence of deamination is the breakdown of amino acids by the action of enzymes on ammonia and a nitrogen-free residue (fatty acids, hydroxy acids, keto acids). Deamination can be in the form of reduction, hydrolytic, oxidative and intramolecular processes. The last two types predominate in humans and animals. 164