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| Clinical data | |
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| Trade names | Cobolmin |
| AHFS/Drugs.com | International Drug Names |
| Routes of administration | By mouth, sublingual, injection. |
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| CompTox Dashboard(EPA) | |
| ECHA InfoCard | 100.033.200 |
| Chemical and physical data | |
| Formula | C63H91CoN13O14P |
| Molar mass | 1344.405 g·mol−1 |
| 3D model (JSmol) | |
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Methylcobalamin (mecobalamin, MeCbl, or MeB12) is acobalamin, a form ofvitamin B12. It differs fromcyanocobalamin in that thecyano group at thecobalt is replaced with amethyl group.[1] Methylcobalamin features an octahedral cobalt(III) centre and can be obtained as bright red crystals.[2] From the perspective ofcoordination chemistry, methylcobalamin is notable as a rare example of a compound that contains metal–alkyl bonds.Nickel–methyl intermediates have been proposed for the final step ofmethanogenesis.
Methylcobalamin can be produced in the laboratory by reducingcyanocobalamin withsodium borohydride in alkaline solution, followed by the addition ofmethyl iodide.[2]
Thisvitamer, along withadenosylcobalamin, is one of two active coenzymes used by vitamin B12-dependent enzymes and is the specific vitamin B12 form used by5-methyltetrahydrofolate-homocysteine methyltransferase (MTR), also known as methionine synthase.[citation needed]
Methylcobalamin participates in theWood-Ljungdahl pathway, which is a pathway by which some organisms utilize carbon dioxide as their source of organic compounds. In this pathway, methylcobalamin provides the methyl group that couples to carbon monoxide (derived from CO2) to affordacetyl-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.[citation needed] It plays an important role in the environment, where it is responsible for thebiomethylation of certainheavy metals. For example, the highly toxicmethylmercury is produced by the action of methylcobalamin.[4] In this role, methylcobalamin serves as a source of "CH3+".
Methylcobalamin is equivalent physiologically to vitamin B12,[5][non-primary source needed] and can be used to prevent or treat pathology arising from a lack of vitamin B12 intake (vitamin B12 deficiency). Methylcobalamin is considered to be equivalent in efficacy to the other vitamin B12vitamers as a dietary supplement, with no clear evidence of differing efficacy between them.[6][7][8]
Methylcobalamin that is ingested is not used directly as a cofactor, but is first converted byMMACHC into cob(II)alamin. Cob(II)alamin is then later converted into the other two forms,adenosylcobalamin and methylcobalamin for use as cofactors. That is, methylcobalamin is first dealkylated and then regenerated.[9][10][11]
Ultra-high-dose intravenous methylcobalamin is researched as treatment ofperipheral neuropathy,diabetic neuropathy, and as a preliminary treatment foramyotrophic lateral sclerosis.[12][13][14][15][16]