The function of ACSM3 (acyl-CoA synthetase medium chain family member 3, Ensembl gene identifier ENSG00000005187) is as follows. Catalyzes the activation of fatty acids by CoA to produce an acyl-CoA, the first step in fatty acid metabolism (PubMed:11772874). Capable of activating medium-chain fatty acids with a preference for isobutyrate among fatty acids with 2-6 carbon atoms (By similarity). .