methylmalonyl CoA mutase B12 binding domain. This domain binds to B12 (adenosylcobamide), which initiates the conversion of succinyl CoA and methylmalonyl CoA by forming an adenosyl radical, which then undergoes a rearrangement exchanging a hydrogen atom with a group attached to a neighboring carbon atom. This family is present in both mammals and bacteria. Bacterial members are heterodimers and involved in the fermentation of pyruvate to propionate. Mammalian members are homodimers and responsible for the conversion of odd-chain fatty acids and branched-chain amino acids via propionyl CoA to succinyl CoA for further degradation.
Jiyao W et al.(2023). "The conserved domain database in 2023.",