Methylmalonic aciduria and homocystinuria type C protein (MMACHC)

Catalyzes the reductive dealkylation of cyanocobalamin to cob(II)alamin, using FAD or FMN as cofactor and NADPH as cosubstrate (PubMed:19700356, PubMed:21697092, PubMed:22642810). Can also catalyze the glutathione-dependent reductive demethylation of methylcobalamin, and, with much lower efficiency, the glutathione-dependent reductive demethylation of adenosylcobalamin (PubMed:19801555, PubMed:22642810, PubMed:25809485).

Under anaerobic conditions cob(I)alamin is the first product; it is highly reactive and is converted to aquocob(II)alamin in the presence of oxygen (PubMed:19801555). Binds cyanocobalamin, adenosylcobalamin, methylcobalamin and other, related vitamin B12 derivatives (PubMed:21071249).