Cobalamin

Cobalamin with the upper axial ligand noted as R

Cobalamin (Cbl) is a general term that is referred to a number of compounds, that have cobalt ion in the middle, hence the name of the compound. Cobalt ion is surrounded by four nitrogen atoms from four tetrapyrrolic corrin rings.^[1]

Cobalamin is a vitamin from the vitamin B group.^[2]

Cobalamin may refer to several chemical forms of vitamin B₁₂, depending on the upper axial ligand of the cobalt ion. These are:

• Cyanocobalamin (R = –CN)
• Hydroxocobalamin (R = –OH)
• Methylcobalamin (R = –CH₃), an active form of vitamin B₁₂
• Adenosylcobalamin (R = –Ado), also an active form of vitamin B₁₂

For dietary supplement purposes, the most commonly used form of B₁₂ vitamin is cyanocobalamin (CNCbl) because it has superior stability, i.e., shelf-life. It was discovered as a factor against pernicious anemia, an illness which is also known as vitamin B₁₂ deficiency anemia. There are also several physiological forms of cobalamin that differ only by the ligand that is attached to cobalt ion. For example, adenosylcobalamin (or cobamamide, AdoCbl) and methylcobalamin (MeCbl) are both cofactors: MeCbl is a cofactor for the Cytosolic methionine synthase; AdoCbl for mitochondrial methylmalonyl-CoA mutase. In physiological conditions an intermediate form of coblalamin is hydroxocobalamin (HOCbl)^[1]

Cobalamin is susceptible to acid. During its biosynthesis, complexes are formed that protect it.

References

See also

• Compound Summary for CID 5311498