DmethylmalonylCoA

D-methylmalonyl-CoA is the D-enantiomer of methylmalonyl-CoA, a CoA thioester important in the metabolism of odd-chain fatty acids, certain amino acids (such as valine, isoleucine, methionine, and threonine), and propionate. The two enantiomers, D- and L-methylmalonyl-CoA, differ in the configuration around the beta carbon, and biological pathways distinguish between them.

Formation and interconversion between enantiomers occur during propionate metabolism. Propionyl-CoA carboxylase converts propionyl-CoA to methylmalonyl-CoA, and the enantiomeric forms can be interconverted by methylmalonyl-CoA racemase in organisms that possess it. In many systems, the D (R) enantiomer is the właściwy substrate for downstream processing, while the L (S) form may require racemization to enter the same pathway.

The primary metabolic fate of methylmalonyl-CoA is determined by methylmalonyl-CoA mutase, a B12-dependent enzyme that converts methylmalonyl-CoA to succinyl-CoA, entering the citric acid cycle. This mutase specifically acts on the R-enantiomer (often associated with the D form), enabling its direct conversion to succinyl-CoA after proper racemization if needed.

Clinical relevance arises when propionyl-CoA carboxylase, methylmalonyl-CoA mutase, or related B12 metabolism is deficient, or when vitamin B12 is deficient. Such defects can lead to methylmalonic acidemia, with accumulation of methylmalonyl-CoA derivatives and methylmalonic acid.

In summary, D-methylmalonyl-CoA is a stereoisomeric intermediate in propionate and odd-chain fatty acid catabolism, linked to the same downstream fate as its L counterpart through racemization and the B12-dependent mutase pathway.