Methylcobalamin (Vitamin B12) (Research Overview)
Methylcobalamin is one of the cobalamins, the group of cobalt-containing corrinoids that make up vitamin B12. It is a small organometallic molecule rather than a peptide: its structure is a tetrapyrrolic corrin ring with a central cobalt ion that carries an upper ligand, here a methyl group, and a lower ligand anchored through a nucleotide loop. The Sealed Peptides listing is a ready-to-use solution of methylcobalamin, molecular weight 1344.4 Da.
Mechanism of Action
In human metabolism two organometallic B12 forms act as coenzymes: methylcobalamin is the cofactor of methionine synthase, which transfers a methyl group from N-methyl-tetrahydrofolate to homocysteine to give methionine, and adenosylcobalamin (coenzyme B12) is the cofactor of methylmalonyl-CoA mutase. The enzymes that depend on cobalamins fall into three families: the adenosylcobalamin-dependent isomerases, the methylcobalamin-dependent methyltransferases and the dehalogenases.
The chemistry differs between these families. In the methyltransferases the cobalt(I) form of the cofactor is the methyl acceptor, and the cobalt-carbon bond is cleaved heterolytically; in the isomerases the same bond is broken homolytically. Reviews of the methyl-transfer chemistry also discuss how the unreactive biological methyl donors are activated.
Research Areas
Organometallic chemistry: methylcobalamin is an organometallic cofactor, and its cobalt-carbon bond is the reactive centre in catalysis. A computational study of the methylcobalamin-dependent methionine synthase describes photolysis of this bond, which generates cob(II)alamin and a methyl radical, and reports it as a side reaction of the enzyme-bound cofactor. The Sealed Peptides listing specifies storage protected from light.
Structure: reviews describe the methyl groups that decorate the corrin ring and distinguish vitamin B12 from other tetrapyrrolic molecules and from its natural analogues, the cobamides.
Findings from published studies describe molecular structure and enzyme chemistry and do not establish safety or efficacy for any indication; they should not be interpreted as medical claims.
What the published literature reports
This section summarizes what published studies report. It describes study designs and results as the authors reported them. It does not describe any use of the research materials sold on this site, and it is not a recommendation, instruction or claim about any product.
Study models and endpoints
- Model Biochemical, structural and computational chemistry of cobalamin-dependent enzymes. [1][2][3][4][5]
- Endpoint Enzyme mechanism, cofactor structure and reaction chemistry. [3][4]
Reported findings
- A review stated that, in humans, methylcobalamin is the cofactor of methionine synthase and adenosylcobalamin is the cofactor of methylmalonyl-CoA mutase. [2]
- A review described the cobalt(I) form of the cofactor as the methyl acceptor in cobalamin-dependent methyl-transfer reactions, including the reaction catalyzed by methionine synthase. [4]
- A review described three subfamilies of cobalamin-dependent enzymes (isomerases, methyltransferases and dehalogenases) and stated that the cobalt–carbon bond ruptures homolytically in the isomerases and heterolytically in the methyltransferases. [3]
- A computational study reported that the photochemistry of methylcobalamin bound to methionine synthase is mediated by low-lying excited states. [5]
Evidence level and limitations
Evidence level: Biochemical, structural and computational literature only. No clinical studies are summarized on this page.
- All cited papers are biochemistry, structural or computational chemistry; none reports a clinical outcome. [1][2][3][4][5]
Not established
- Clinical studies of vitamin B12 forms exist in the wider literature but are not summarized on this page; the cited biochemistry review does not address clinical outcomes. [2]
Summaries of published literature, not claims about any product sold here. For laboratory research use only.
Specification summary
B12 25mg 10ml
Stated purity ≥99%. For laboratory research use only.
Related materials
Laboratory background
Education for people working with this material in the laboratory: guides on handling and analysis, definitions of terms, and arithmetic tools. It describes no use of the material.
Guides
Glossary terms
References
- Mathur Y, Hazra AB. Methylations in vitamin B(12) biosynthesis and catalysis. Curr Opin Struct Biol. 2022;77:102490. PMID 36371846 · DOI
- Kräutler B. Biochemistry of B12-cofactors in human metabolism. Subcell Biochem. 2012;56:323-46. PMID 22116707 · DOI
- Banerjee R, Ragsdale SW. The many faces of vitamin B12: catalysis by cobalamin-dependent enzymes. Annu Rev Biochem. 2003;72:209-47. PMID 14527323 · DOI
- Matthews RG. Cobalamin-dependent methyltransferases. Acc Chem Res. 2001;34(8):681-9. PMID 11513576 · DOI
- Ghosh AP, Mamun AA, Lodowski P, Jaworska M, Kozlowski PM. Mechanism of the photo-induced activation of CoC bond in methylcobalamin-dependent methionine synthase. J Photochem Photobiol B. 2018;189:306-317. PMID 30447559 · DOI
Cited literature is provided for scientific context only and does not describe or endorse any use of these products.
For laboratory research use only. Not for human or veterinary use. Not intended to diagnose, treat, cure, or prevent any disease.