Vitamin B₁₂: chemistry and biochemistry

Vitamin B₁₂, the ‘antipernicious anaemia factor’, is required for human and animal metabolism. It was discovered in the late 1940s and its unique corrin ligand was revealed approx. 10 years later by X-ray crystallography. The B₁₂-coenzymes are cofactors in various important enzymatic reactions and are particularly relevant in the metabolism of anaerobic microorganisms. Microorganisms are the only natural sources of the B₁₂-derivatives, whereas most spheres of life (except for the higher plants) depend on these cobalt corrinoids.