Cobalamins

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.