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Cited by 88Porphyrin Metabolism and DisordersFolate and B Vitamins ResearchMetalloenzymes and iron-sulfur proteins

Coenzyme B12 (cobalamin)-dependent enzymes

Neil, E., Marsh, G.·1999·Essays in Biochemistry
DOI 10.1042/bse0340139
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Abstract

The B12 or cobalamin coenzymes are complex macrocycles whose reactivity is associated with a unique cobalt-carbon bond. The two biologically active forms are MeCbl and AdoCbl and their closely related cobamide forms. MeCbl participates as the intermediate carrier of activated methyl groups. During the catalytic cycle the coenzyme shuttles between MeCbl and the highly nucleophilic cob(I)alamin form. Examples of MeCbl-dependent enzymes include methionine synthase and Me-H4-MPT: coenzyme M methyl transferase. AdoCbl functions as a source of carbon-based free radicals that are unmasked by homolysis of the coenzyme's cobalt-carbon bond. The free radicals are subsequently used to remove non-acid hydrogen atoms from substrates to facilitate a variety of reactions involving cleavage of carbon-carbon, carbon-oxygen and carbon-nitrogen bonds. Most reactions involve 1,2 migrations of hydroxy-, amino- and carbon-containing groups, but there is also one class of ribonucleotide reductases that uses AdoCbl. The structures of two cobalamin-dependent enzymes, methionine synthase and methylmalonyl-CoA mutase, have been solved. In both cases the cobalt is co-ordinated by a histidine ligand from the protein. The significance of this binding motif is presently unclear since in other cobalamin-dependent enzymes spectroscopic evidence suggests that the coenzyme's nucleotide 'tail' remains co-ordinated to cobalt when bound to the protein.

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  • The most recognized biochemical role of Co is as a cofactor in cobalamin (vitamin B12), which is essential for metalloenzymes including methionine synthase and ribonucleotide reductase.

    “The most recognized biochemical role of cobalt (Co) is its participation as a cofactor in cobalamin (vitamin B12), which is essential for a number of metalloenzymes, including methionine synthase and ribonucleotide reductase”

    From Trace elements at the intersection of marine biological and geochemical evolution (2016) · cites this paper as Marsh, 1999

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Authors
Neil, E., & Marsh, G.
Affiliations
  • University of Michigan (US)
  • Department of Chemistry, University of Michigan, Ann Arbor 48109-1055, USA.
Venue
Essays in Biochemistry
Publisher
Portland Press Ltd.
Published
1999-11-01
Volume
34
Pages
139-154
ISSN
  • 0071-1365 (ISSN-L)
  • 1744-1358
DOI
10.1042/bse0340139
OpenAlex
W263758105
Cited by
88
References
23
Citations by year
2026: 2 · 2025: 3 · 2024: 2 · 2023: 5 · 2022: 3 · 2021: 4 · 2020: 6 · 2019: 4 · 2018: 2 · 2017: 3 · 2016: 1 · 2015: 2 · 2014: 1 · 2013: 2 · 2012: 4
FWCI
1.27
Type
journal article
Language
en
Open access
closed
Locations
  • Essays in Biochemistry (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institutes of Health (5r29gm055163-02)
  • National Institute of General Medical Sciences (GM 55163)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Porphyrin Metabolism and Disorders
  • Health Sciences › Medicine › Rheumatology › Folate and B Vitamins Research
  • Physical Sciences › Energy › Renewable Energy, Sustainability and the Environment › Metalloenzymes and iron-sulfur proteins
Keywords
vitamin B12, coenzyme B12, methylcobalamin, adenosylcobalamin, cobalt-carbon bond, methionine synthase, methylmalonyl-CoA mutase, methyltransferase, cobamide, ribonucleotide reductase, 1,2-hydrogen shift, enzyme structure
MeSH terms
Cobamides, Enzymes, Humans, Methylmalonyl-CoA Mutase, Models, Molecular, 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase, Vitamin B 12

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