MLYCD, also named as MCD, is a 50-55 kDa protein. It is an enzyme that catalyzes the conversion of malonyl-CoA to acetyl-CoA. In the fatty acid biosynthesis MCD selectively removes malonyl-CoA and thus assures that methyl-malonyl-CoA is the only chain elongating substrate for fatty acid synthase and that fatty acids with multiple methyl side chains are produced. In peroxisomes it may be involved in degrading intraperoxisomal malonyl-CoA, which is generated by the peroxisomal beta-oxidation of odd chain-length dicarboxylic fatty acids. 66 kDa MLYCD protein has been identified in normal cell lines. Some patients give the 68-83 kDa smeary band. (PMID:12955715)