Adenosylcobalamin (AdoCbl), also known as coenzyme B₁₂, cobamamide, and dibencozide, is, along with

methylcobalamin Methylcobalamin (mecobalamin, MeCbl, or MeB) is a cobalamin, a form of vitamin B. It differs from cyanocobalamin in that the cyano group at the cobalt is replaced with a methyl group. Methylcobalamin features an octahedral cobalt(III) centre and ...

(MeCbl), one of the biologically active forms of vitamin B₁₂. Adenosylcobalamin participates as a cofactor in radical-mediated 1,2-carbon skeleton rearrangements. These processes require the formation of the

deoxyadenosyl radical A deoxyadenosyl radical is a free radical that is structurally related to adenosine by removal of a 5′-hydroxy group from adenosine. This radical occurs in nature as a reactive intermediate. It is generated by radical SAM Radical SAM is a desig ...

through homolytic dissociation of the carbon-cobalt bond. This bond is exceptionally weak, with a bond dissociation energy of 31 kcal/mol, which is further lowered in the chemical environment of an enzyme active site. An

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

that uses adenosylcobalamin as a cofactor is

methylmalonyl-CoA mutase Methylmalonyl-CoA mutase (, MCM), mitochondrial, also known as methylmalonyl-CoA isomerase, is a protein that in humans is encoded by the ''MUT'' gene. This vitamin B12-dependent enzyme catalyzes the isomerization of methylmalonyl-CoA to succiny ...

(MCM). Further experimentation has also determined adenosylcobalamin's role in regulating expression of some bacterial genes. By binding to CarH, AdoCbl can modulate carotenoid genes, which confer warm colors onto various plants. Carotenoid transcription is activated by sunlight, due to the response from AdoCbl. There are other photoreceptors across different bacterial communities, aside from CarH, that also have reactive capability when bound to AdoCbl. For instance, AerR is another factor that uses AdoCbl to give off purple pigmentation. Additional examination of adenosylcobalamin-bound enzymes and the development of this cofactor over time may prove to hold regulatory function of DNA and RNA.

References

External links

* {{Vitamin B vitamins Cofactors Organocobalt compounds Vitamers Vitamin B12

See also

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