Methylmalonyl coenzyme A (methylmalonyl-CoA) is an intermediate in multiple metabolic pathways in bacteria and eukaryotes. It is an intermediate in carbon assimilation in certain bacteria and carbon fixation in plants. Methylmalonyl-CoA is converted to succinyl-CoA by methylmalonyl-CoA mutase with vitamin B12 as a coenzyme. A deficiency in vitamin B12 leads to a build-up of methylmalonyl-CoA.
