Biosynthesis of medium chain fatty acids in Drosophila melanogaster.

Adult Drosophila melanogaster synthesizes dodecanoic and tetradecanoic acids in vivo, along with the more common 16- and 18-carbon fatty acids. The radiolabeled C12 and C14 fatty acids synthesized from sodium [1-14C]acetate are found primarily in the diacylglycerol and triacylglycerol fractions. Partially purified fatty acid synthetase (FAS) synthesizes C14, C16, and C18 fatty acids (as the free acids) at 0.2 M ionic strength. Increasing the ionic strength to 2.0 M causes partially purified FAS to synthesize primarily C12 and C14 fatty acids. Addition of aliquots of the microsomal pellet and other soluble protein fractions does not alter the pattern of fatty acids synthesized by FAS. The percentage of C12 and C14 fatty acids synthesized at high ionic strength by individual fractions from the FAS peak (Sepharose 6B column) is constant across the peak. None of the soluble protein fractions is able to relieve the inhibition of FAS by phenylmethylsulfonyl fluoride. These results indicate that the FAS of D. melanogaster has the inherent capability to form C12 and C14 fatty acids and that no other soluble protein appears to be involved in their synthesis.