Cobalamines - Organometallics in Nature

With the possible exception of the redox enzymes cytochrome P-450 (iron) and the methanogenic bacterial cofactor F-430 (nickel) [5-7], the cobalamines are the only 

Vitamin B12 (2 a) participates in the aqueous-phase biosynthesis of purine and pyrimidine bases, the reduction of ribonucleotide triphosphates, the conversion of methylmalonyl-coenzyme A to succinyl-coenzyme A, the biosynthesis of methionine from homocysteine, and the formation of myelin sheath in the nervous systems. 

Coenzyme B12 catalyzes the 1,2-shift of alkyl groups (isomerase reaction) in hydrocarbons. An extensive chemistry was based on the reactivity aspects, where co-balamins acted as model systems, mainly in the work of Schrauzer et al. [8]. 

There is a considerable demand for research on organometallic species generated in living organisms (cf. Section 6.15). Apart from the analogies with the chemistry of vitamin B12, hardly any research has been concluded in this area. 

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