COBAMIDE COENZYMES. COBALAMINS (VITAMIN B12)

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Annotatsiya.  Reactions in which cobamide coenzymes take part are conventionally divided into two groups.

Cobalamins enter the human body with food. Liver, kidneys, eggs, and milk are rich in them. Plant foods are poor in cobalamins. Part of the vitamin B12 is produced by intestinal bacteria. An adult's daily requirement for the vitamin is about 2 mcg. Vitamin B12 was discovered in 1958 by Barker. In the vitamin molecule, the central cobalt atom is bonded to the nitrogen atoms of the four reduced pyrrole rings, forming a porphyrin-like corrin nucleus, and to the nitrogen atom of 5,6-dimethylbenzimidazole (Figure 17). The cobalt-containing part of the vitamin molecule is a planar (planar) figure; Perpendicular to it is a nucleotide ligand, which, in addition to 5,6-dimethylbenzimidazole, contains ribose and phosphate residue in 3rd carbon atom. Vitamin B12 derivatives containing OH group (oxycobalamin), chlorine (chlorocobalamin),_{H2O (}aquacobalamin) and nitrous acid (nitrithocobalamin) were obtained.