Methylmalonyl CoA epimerase

Methylmalonyl CoA epimerase (EC 5.1.99.1) is an enzyme which in humans is encoded by the MCEE gene. It is involved in the process of breaking down fatty acids (fatty acid catabolism). It is also frequently called methylmalonyl-CoA racemase, but this is technically inaccurate. It is not a racemase because the CoA moiety has 5 other stereocenters. Outside of humans, the term "Methylmalonyl-CoA epimerase" is sometimes used more broadly to refer to any enzyme that can catalyze the same reaction, such as the multifunctional enzyme called "Ethylmalonyl-CoA/methylmalonyl-CoA epimerase", which was found in a type of bacteria.

Structure

The "MCEE" gene is located in the 2p13 region and contains 4 exons, and encodes for a protein that is approximately 18 kDa in size and located to the mitochondrial matrix. Several natural variants in amino acid sequences exist. The structure of the MCEE protein has been resolved by X-ray crystallography at 1.8-angstrom resolution.

Function

The MCEE gene encodes an enzyme that interconverts D- and L- methylmalonyl-CoA during the degradation of branched-chain amino acids, odd chain-length fatty acids, and other metabolites. In biochemistry terms, it catalyses the chemical reaction that converts (S)-methylmalonyl-CoA to the (R) form:

(S)-methylmalonyl-CoA

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{\displaystyle \rightleftharpoons }

(R)-methylmalonyl-CoA

Methylmalonyl CoA epimerase plays an important role in the catabolism of fatty acids with odd-length carbon chains.