Molecular characterization and expression of rat acyl-CoA synthetase 3

Isolation and characterization of a rat brain cDNA identified a third acyl-CoA synthetase (ACS) designated ACS3. The deduced amino acid sequence of the cDNA revealed that ACS3 consists of 720 amino acids and exhibits a structural architecture common to ACSs from various origins. ACS3 expressed in COS cells was purified to near homogeneity. The purified ACS3 resolved by SDS-polyacrylamide gel electrophoresis into two major proteins of 79 and 80 kDa. Cell-free translation of a synthetic mRNA encoding the entire region of ACS3 revealed that the two isoforms were derived from the same mRNA. The purified ACS3 utilizes laurate and myristate most efficiently among C8-C22 saturated fatty acids and arachidonate and eicosapentaenoate among C16-C20 unsaturated fatty acids. Northern blot analysis revealed that ACS3 mRNA is most abundant in brain and, to a much lesser extent, in lung, adrenal gland, kidney, and small intestine. During the development of the rat brain, expression of ACS3 mRNA reached a maximum level at 15 days after birth and then declined gradually to 10% of the maximum in the adult brain.