Chemistry:Methylcobalamin
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| Trade names | Cobolmin |
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| Routes of administration | By mouth, sublingual, injection. |
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| Formula | C63H91CoN13O14P |
| Molar mass | 1344.405 g·mol−1 |
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Methylcobalamin (mecobalamin, MeCbl, or MeB12) is a cobalamin, a form of vitamin B12. It differs from cyanocobalamin in that the cyano group at the cobalt is replaced with a methyl group.[1] Methylcobalamin features an octahedral cobalt(III) centre and can be obtained as bright red crystals.[2] From the perspective of coordination 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 of methanogenesis.
Methylcobalamin is equivalent physiologically to vitamin B12,[3] and can be used to prevent or treat pathology arising from a lack of vitamin B12 intake (vitamin B12 deficiency).
Methylcobalamin is also used in the treatment of peripheral neuropathy, diabetic neuropathy, and as a preliminary treatment for amyotrophic lateral sclerosis.[4]
Methylcobalamin that is ingested is not used directly as a cofactor, but is first converted by MMACHC 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.[5][6][7]
According to one author, it is important to treat vitamin B12 deficiency with hydroxocobalamin or cyanocobalamin or a combination of adenosylcobalamin and methylcobalamin, and not methylcobalamin alone.[8]
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, along with adenosylcobalamin, 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.[citation needed]
Methylcobalamin participates in the Wood-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 afford acetyl-CoA. Acetyl-CoA is a derivative of acetic acid that is converted to more complex molecules as required by the organism.[9]
Methylcobalamin is produced by some bacteria.[citation needed] It plays an important role in the environment, where it is responsible for the biomethylation of certain heavy metals. For example, the highly toxic methylmercury is produced by the action of methylcobalamin.[10] In this role, methylcobalamin serves as a source of "CH3+".
A lack of cobalamin can lead to megaloblastic anemia and subacute combined degeneration of the spinal cord.[11]
See also
References
- ↑ Vitamins in animal and human nutrition. Wiley. 2000. ISBN 978-0813826301. https://books.google.com/books?id=dXOPBMYIPcQC&pg=PA526. Retrieved 28 January 2018.
- ↑ 2.0 2.1 David, Dophin (January 1971). "Preparation of the Reduced Forms of Vitamin B12 and of Some Analogs of the Vitamin B12 Coenzyme Containing a Cobalt-Carbon Bond". Vitamins and Coenzymes. Methods in Enzymology. 18. Academic Press. pp. 34–54. doi:10.1016/S0076-6879(71)18006-8. ISBN 9780121818821.
- ↑ "A randomized, open labeled study comparing the serum levels of cobalamin after three doses of 500 mcg vs. a single dose methylcobalamin of 1500 mcg in patients with peripheral neuropathy". The Korean Journal of Pain 31 (3): 183–190. July 2018. doi:10.3344/kjp.2018.31.3.183. PMID 30013732.
- ↑ "Eisai Submits New Drug Application for Mecobalamin Ultra-High Dose Preparation as Treatment for Amyotrophic Lateral Sclerosis in Japan". http://www.eisai.com/news/enews201535pdf.pdf.
- ↑ "A human vitamin B12 trafficking protein uses glutathione transferase activity for processing alkylcobalamins". The Journal of Biological Chemistry 284 (48): 33418–33424. November 2009. doi:10.1074/jbc.M109.057877. PMID 19801555.
- ↑ "Processing of alkylcobalamins in mammalian cells: A role for the MMACHC (cblC) gene product". Molecular Genetics and Metabolism 97 (4): 260–266. August 2009. doi:10.1016/j.ymgme.2009.04.005. PMID 19447654.
- ↑ "Genetic disorders of vitamin B₁₂ metabolism: eight complementation groups–eight genes". Expert Reviews in Molecular Medicine 12: e37. November 2010. doi:10.1017/S1462399410001651. PMID 21114891.
- ↑ "Treatment of vitamin B12 deficiency – Methylcobalamine? Cyancobalamine? Hydroxocobalamin? – clearing the confusion". European Journal of Clinical Nutrition 69 (1): 1–2. January 2015. doi:10.1038/ejcn.2014.165. PMID 25117994.
- ↑ "Structure-function relationships of anaerobic gas-processing metalloenzymes". Nature 460 (7257): 814–822. August 2009. doi:10.1038/nature08299. PMID 19675641. Bibcode: 2009Natur.460..814F.
- ↑ Comprehensive B12: Chemistry, Biochemistry, Nutrition, Ecology, Medicine, Walter de Gruyter, 1987, ISBN 978-3110082395, https://books.google.com/books?id=OBlxCKbYCx8C&pg=PA32
- ↑ "Vitamins Deficiencies and Brain Function". Neurochemical Mechanisms in Disease. Advances in Neurobiology. 1. 2011. pp. 103-124 (112). doi:10.1007/978-1-4419-7104-3_4. ISBN 978-1-4419-7103-6.
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