Cob(I)yrinic acid a,c-diamide adenosyltransferase, mitochondrial is an enzyme that in humans is encoded by the MMAB gene.
This gene encodes an enzyme (cob(I)yrinic acid a,c-diamide adenosyltransferase) that catalyzes the final step in the conversion of vitamin B<sub>12</sub> into adenosylcobalamin (AdoCbl), a vitamin B<sub>12</sub>-containing coenzyme for methylmalonyl-CoA mutase.
Mutations in the gene are the cause of vitamin B<sub>12</sub>-dependent methylmalonic aciduria linked to the cblB complementation group.