Coenzyme B12-dependent-methylmalonyl coenzyme A (CoA) mutase (MCM) family, isobutyryl-CoA mutase (ICM)-like subfamily; contains archaeal and bacterial proteins similar to the large subunit of Streptomyces cinnamonensis coenzyme B12-dependent ICM. ICM from S. cinnamonensis is comprised of a large and a small subunit. The holoenzyme appears to be an alpha2beta2 heterotetramer with up to 2 molecules of coenzyme B12 bound. The small subunit binds coenzyme B12. ICM catalyzes the reversible rearrangement of n-butyryl-CoA to isobutyryl-CoA, intermediates in fatty acid and valine catabolism, which in S. cinnamonensis can be converted to methylmalonyl-CoA and used in polyketide synthesis.
Jiyao W et al.(2023). "The conserved domain database in 2023.",