Vitamin B12 What is it

Cyanocobalamin (la) is a relatively inert complex and, apart from being involved in the detoxification of small amounts of hydrogen cyanide [5], does not appear to serve any major biological function [10]. The only difference between this species and the metabolically active forms of B12 (methylcobalamin (MeCbl Ib) and 5 -deoxyadenosylcobalamin (AdoCbl Ic)) is the ligand that occupies the 

A striking feature of the B12 complexes (la, Ib, and Ic) is the presence of a naturally-occurring cobalt-carbon bond. The rarity of a water-stable example of such a bond led Abeles to predict that in this bond probably lies the secret of its reactivity [11]. Indeed, as we shall see later, there is now substantial support for this insightful prediction. 

---