Reaction: Defective MMAA does not protect MUT
- in pathway: Defective MMAA causes MMA, cblA type
Methylmalonic aciduria type A protein (MMAA) is thought to act as a chaperone to MUT, the enzyme which utilises adenosylcobalamin (AdoCbl) as a cofactor. MMAA is suggested to play a dual role with regards to MUT protection and reactivation. Some AdoCbl-dependent enzymes undergo suicide inactivation after catalysis due to the oxidative inactivation of Cbl. MMAA is thought to play a protective role to prevent MUT being inactivated in this way. Defects in MMAA cause methylmalonic aciduria type cblA (cblA 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. Mutations causing cblA include MMAA Q95*, R145*, Y207C and D87Ifs*11 (Dobson et al. 2002, Lerner-Ellis et al. 2004).
Reaction - small molecule participants:
AdoCbl [mitochondrial matrix]
Reactome.org reaction link: R-HSA-3322135
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Reaction input - small molecules:
cobamamide
Reaction output - small molecules:
Reactome.org link: R-HSA-3322135