What is the difference between MMA and MMA Cbl-C?
MMA and Cbl-C are both (autosomal recessive) enzyme deficiencies that cause a block in the same metabolic pathway, namely the conversion of L-methyl malonyl CoA to succinyl CoA. The enzyme missing in classical MMA is methylmalonyl CoA mutase. To do its job correctly, this methylmalonyl CoA mutase requires what is called a “cofactor” or “coenzyme” called adenosyl cobalamin, which is a derivative of vitamin B12. Cbl-C is due to a defect in an enzyme involved in the production of this necessary cofactor, adenosylcobalamin. So some persons with methylmalonic acidemia have a mutation in one of the genes involved in cobalamin synthesis rather than in the mutase enzyme. The effect is the same except Cbl-C may also cause additional symptoms of another disorder called homocystinuria since the same cobalamin cofactor is also required in another pathway, the homocysteine metabolic pathway.
