Also found in: Dictionary, Thesaurus, Medical.
natural biologically active organic cobalt compounds.
The structural base of the cobalamins is a corrin ring consisting of four pyrrole nuclei in which the nitrogen atoms are bonded to a central cobalt atom. The three most well known cobalamins, which differ in the type of substituent for the cobalt atom, are cyanocobalamin, or vitamin B12, and its coenzymes methylcobalamin and 5’-deoxyadenosylcobalamin. Vitamin B12 is a metabolic product of intestinal flora. In man or animals, avitaminosis B12 develops if the absorption of B12 is impaired for any reason. Cobalamins are deposited in the liver in the form of 5’-deoxyadenosylcobalamin, which takes part in a number of enzymic reactions that are accompanied by intramolecular rearrangements. Methylcobalamin is involved in the biosynthesis of the amino acid methionine, methane, and acetic acid. Vitamin B12 is produced industrially by microbiological synthesis.