Coenzyme B12-dependent-methylmalonyl coenzyme A (CoA) mutase (MCM) family, unknown subfamily 1; composed of uncharacterized bacterial proteins containing a C-terminal MCM domain. MCM catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA. The reaction proceeds via radical intermediates beginning with a substrate-induced homolytic cleavage of the Co-C bond of coenzyme B12 to produce cob(II)alamin and the deoxyadenosyl radical. MCM plays an important role in the conversion of propionyl-CoA to succinyl-CoA during the degradation of propionate for the Krebs cycle. In some bacteria, MCM is involved in the reverse metabolic reaction, the rearrangement of succinyl-CoA to methylmalonyl-CoA. Members of this subfamily also contain an N-terminal coenzyme B12 binding domain followed by a domain similar to the E. coli ArgK membrane ATPase.
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