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Methylcobalamin
Form of vitamin B12

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. Methylcobalamin features an octahedral cobalt(III) centre and can be obtained as bright red crystals. 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.

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Production

Methylcobalamin can be produced in the laboratory by reducing cyanocobalamin with sodium borohydride in alkaline solution, followed by the addition of methyl iodide.3

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.

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.4

Methylcobalamin is produced by some bacteria. 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.5 In this role, methylcobalamin serves as a source of "CH3+".

Role in human health

Methylcobalamin is equivalent physiologically to vitamin B12,6[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 B12 vitamers as a dietary supplement, with no clear evidence of differing efficacy between them.789

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.101112

Research directions

Ultra-high-dose intravenous methylcobalamin is researched as treatment of peripheral neuropathy, diabetic neuropathy, and as a preliminary treatment for amyotrophic lateral sclerosis.1314151617

See also

References

  1. McDowell LR (2000). Vitamins in animal and human nutrition. Wiley. ISBN 978-0813826301. Retrieved 28 January 2018 – via Booksgoogle.com. 978-0813826301 ↩

  2. David D (January 1971). "Preparation of the Reduced Forms of Vitamin B12 and of Some Analogs of the Vitamin B12 Coenzyme Containing a Cobalt-Carbon Bond". In McCormick DB, Wright LD (eds.). Vitamins and Coenzymes. Methods in Enzymology. Vol. 18. Academic Press. pp. 34–54. doi:10.1016/S0076-6879(71)18006-8. ISBN 9780121818821. 9780121818821 ↩

  3. David D (January 1971). "Preparation of the Reduced Forms of Vitamin B12 and of Some Analogs of the Vitamin B12 Coenzyme Containing a Cobalt-Carbon Bond". In McCormick DB, Wright LD (eds.). Vitamins and Coenzymes. Methods in Enzymology. Vol. 18. Academic Press. pp. 34–54. doi:10.1016/S0076-6879(71)18006-8. ISBN 9780121818821. 9780121818821 ↩

  4. Fontecilla-Camps JC, Amara P, Cavazza C, Nicolet Y, Volbeda A (August 2009). "Structure-function relationships of anaerobic gas-processing metalloenzymes". Nature. 460 (7257): 814–822. Bibcode:2009Natur.460..814F. doi:10.1038/nature08299. PMID 19675641. S2CID 4421420. /wiki/Bibcode_(identifier) ↩

  5. Schneider Z, Stroiński A (1987), Comprehensive B12: Chemistry, Biochemistry, Nutrition, Ecology, Medicine, Walter de Gruyter, ISBN 978-3110082395 978-3110082395 ↩

  6. Sil A, Kumar H, Mondal RD, Anand SS, Ghosal A, Datta A, et al. (July 2018). "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. doi:10.3344/kjp.2018.31.3.183. PMC 6037815. PMID 30013732.[non-primary source needed] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6037815 ↩

  7. Aguilar F, Charrondiere U, Dusemund B, Galtier P, Gilbert J, Gott DM, et al. (European Food Safety Authority) (25 September 2008). "5′-deoxyadenosylcobalamin and methylcobalamin as sources for Vitamin B12 added as a nutritional substance in food supplements: Scientific opinion of the Scientific Panel on Food Additives and Nutrient Sources added to food". EFSA Journal. 815 (10): 1–21. doi:10.2903/j.efsa.2008.815. /wiki/European_Food_Safety_Authority ↩

  8. Obeid R, Fedosov SN, Nexo E (28 March 2015). "Cobalamin coenzyme forms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamin deficiency". Molecular Nutrition & Food Research. 59 (7): 1364–1372. doi:10.1002/mnfr.201500019. PMC 4692085. PMID 25820384. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4692085 ↩

  9. Obeid R, Andrès E, Češka R, Hooshmand B, Guéant-Rodriguez R, Prada GI, et al. (10 April 2024). "Diagnosis, Treatment and Long-Term Management of Vitamin B12 Deficiency in Adults: A Delphi Expert Consensus". Journal of Clinical Medicine. 13 (8): 2176. doi:10.3390/jcm13082176. PMC 11050313. PMID 38673453. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11050313 ↩

  10. Kim J, Hannibal L, Gherasim C, Jacobsen DW, Banerjee R (November 2009). "A human vitamin B12 trafficking protein uses glutathione transferase activity for processing alkylcobalamins". The Journal of Biological Chemistry. 284 (48): 33418–33424. doi:10.1074/jbc.M109.057877. PMC 2785186. PMID 19801555. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2785186 ↩

  11. Hannibal L, Kim J, Brasch NE, Wang S, Rosenblatt DS, Banerjee R, et al. (August 2009). "Processing of alkylcobalamins in mammalian cells: A role for the MMACHC (cblC) gene product". Molecular Genetics and Metabolism. 97 (4): 260–266. doi:10.1016/j.ymgme.2009.04.005. PMC 2709701. PMID 19447654. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2709701 ↩

  12. Froese DS, Gravel RA (November 2010). "Genetic disorders of vitamin B₁₂ metabolism: eight complementation groups–eight genes". Expert Reviews in Molecular Medicine. 12: e37. doi:10.1017/S1462399410001651. PMC 2995210. PMID 21114891. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2995210 ↩

  13. "Eisai Submits New Drug Application for Mecobalamin Ultra-High Dose Preparation as Treatment for Amyotrophic Lateral Sclerosis in Japan" (PDF). Eisai.com. Archived (PDF) from the original on 17 April 2016. Retrieved 28 January 2018. http://www.eisai.com/news/enews201535pdf.pdf ↩

  14. Naik SU, Sonawane DV (April 2015). "Methylcobalamine is effective in peripheral neuropathies". European Journal of Clinical Nutrition. 69 (4): 530. doi:10.1038/ejcn.2014.281. PMID 25585598. /wiki/Doi_(identifier) ↩

  15. Vyloppilli S, Thangavelu A, Vichattu SV, Sayd S (August 2021). "Safety and efficacy of methylcobalamin in the treatment of peripheral nerve injuries and diabetic neuropathies-A systematic review" (PDF). Acta Scientific Pharmaceutical Sciences. 5 (8): 75–80. doi:10.31080/ASPS.2021.05.0769. Archived (PDF) from the original on 27 September 2023. Retrieved 8 March 2025. https://actascientific.com/ASPS/pdf/ASPS-05-0769.pdf ↩

  16. Deng H, Yin J, Zhang J, Xu Q, Liu X, Liu L, et al. (August 2014). "Meta-analysis of methylcobalamin alone and in combination with prostaglandin E1 in the treatment of diabetic peripheral neuropathy". Endocrine. 46 (3): 445–454. doi:10.1007/s12020-014-0181-6. PMID 24522613. Archived from the original on 28 April 2023. Retrieved 8 March 2025. https://link.springer.com/article/10.1007/s12020-014-0181-6 ↩

  17. Kaji R, Imai T, Iwasaki Y, Okamoto K, Nakagawa M, Ohashi Y, et al. (April 2019). "Ultra-high-dose methylcobalamin in amyotrophic lateral sclerosis: a long-term phase II/III randomised controlled study". Journal of Neurology, Neurosurgery, and Psychiatry. 90 (4): 451–457. doi:10.1136/jnnp-2018-319294. PMC 6581107. PMID 30636701. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6581107 ↩