Methylmalonyl-CoA mutase (MUT aka MCM) (Jansen et al. 1989) utilises adenosylcobalamin (AdoCbl) as a cofactor and catalyses interchange of a carbonyl-CoA group and a hydrogen atom in conversion of methymalonyl-CoA to form succinyl-CoA, a precursor for the citric acid cycle. MUT has a homodimeric structure and is located in the mitochondrial matrix. Defects in MUT cause methylmalonic aciduria type mut (MMAM; MIM:251000), an often fatal disorder of organic acid metabolism (Worgan et al. 2006).
Methylmalonic aciduria type A protein (MMAA) (Dobson et al. 2002) is thought to act as a chaperone to MUT and is suggested to play a dual role with regards to MUT protection and reactivation.
Defects in MMAA cause methylmalonic aciduria type cblA (MMAA aka methylmalonic aciduria type A or vitamin B12-responsive methylmalonicaciduria of cblA complementation type; MIM:251100). Affected individuals accumulate methylmalonic acid in the blood and urine and are prone to potentially life threatening acidotic crises in infancy or early childhood (Dobson et al. 2002, Lerner-Ellis et al. 2004).