Coenzyme B12 serves as a cofactor in various enzymatic reactions in which a hydrogen atom is interchanged with a substituent on an adjacent carbon atom. Measurement of the dissociation energy of the coenzyme's cobalt-carbon bond and studies of the rearrangement of model free radicals related to those derived from methylmalonyl-coenzyme A suggest that these enzymatic reactions occur through homolytic dissociation of the coenzyme's cobalt-carbon bond, abstraction of a hydrogen atom from the substrate by the coenzyme-derived 5′-deoxyadenosyl radical, and rearrangement of the resulting substrate radical. The only role thus far identified for coenzyme B12 in these reactions - namely, that of a free radical precursor - reflects the weakness, and facile dissocation, of the cobalt-carbon bond.
CITATION STYLE
Halpern, J. (1985). Mechanisms of coenzyme B12-dependent rearrangements. Science, 227(4689), 869–875. https://doi.org/10.1126/science.2857503
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