Methylcobalamin

Methylcobalamin

Systematic (IUPAC) name
carbanide; cobalt(3+);
Clinical data
AHFS/Drugs.com	International Drug Names
Pregnancy cat.	?
Legal status	?
Routes	oral,sublingual,injection.
Identifiers
CAS number	13422-55-4 Y
ATC code	B03BA05
PubChem	CID 6436232
UNII	BR1SN1JS2W N
ChEMBL	CHEMBL1697757 N
Chemical data
Formula	C63H91CoN13O14P
Mol. mass	1344.40 g/mol
N (what is this?)  (verify)

Methylcobalamin (mecobalamin, MeCbl, or MeB₁₂) is a cobalamin used in the treatment of peripheral neuropathy, diabetic neuropathy, and as a preliminary treatment for amyotrophic lateral sclerosis. It is a form of vitamin B₁₂ and differs from cyanocobalamin in that the cyanide is replaced by a methyl group.^[1] Methylcobalamin features an octahedral cobalt(III) centre. Methylcobalamin can as obtained as bright red crystals.^[2]

From the perspective of coordination chemistry, methylcobalamin is notable as a rare example of an enzyme that contains metal-alkyl bonds. Nickel-methyl intermediates have been proposed for the final step of methanogenesis.

Production

Methylcobalamin can be produced in the laboratory by reducing cyanocobalamin with sodium borohydride in alkaline solution, followed by the addition of methyl iodide.^[2]

Functions

This vitamer is one of two active coenzymes used by vitamin B₁₂-dependent enzymes and is the specific vitamin B₁₂ form used by 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), also known as methionine synthase. In physiological terms, it is equivalent to vitamin B₁₂, e.g. for addressing pathologies arising from a lack of vitamin B₁₂, such as pernicious anemia.

Methylcobalamin participates in the Wood-Ljungdahl pathway, which is a pathway by which some organisms utilize carbon dioxide as their source of organic ompounds. In this pathway, methylcobalamin provides the methyl group that couples to carbon monoxide (derived from CO₂) to afford acetyl-CoA. Acetyl-CoA is a derivative of acetic acid that is converted to more complex molecules as required by the organism.^[3]

Methylcobalamin is produced by some bacteria. It plays an important role in the environment. In the environment, it is responsible for the biomethylation of certain heavy metals. For example, the highly toxic methylmercury is produced by the action of methylcobalamin.^[4] In this role, methylcobalamin serves as a source "CH₃⁺".

See also

• Cobamamide
• Cyanocobalamin
• Hydroxocobalamin
• Vitamin B12

References

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