METHYL-BRANCHED FATTY-ACID BIOSYNTHESIS IN TRIATOMA-INFESTANS

Fatty acid synthetase (FAS) activity was found both in the microsomal and cytosolic fractions of the egg of the Hemiptera Triatoma infestans . Major fatty acids are oleic and palmitic acids, Minor amounts of n-v ery long chain fatty acids (up to 26 carbons) are present together wit h trace amounts of methyl-branched fatty acids, The microsomal FAS act ivity was separated from the elongation activity by solubilization wit h 0.75 M KCl. The microsomal FAS is able to incorporate methylmalonyl- CoA in the absence of malonyl-CoA whereas the soluble FAS is not, Meth ylmalonyl-CoA incorporation by microsomal FAS is much more efficient t han by the soluble form, The only product of both FASs, after incubati on with [C-14]malonyl-CoA or [H-3]acetyl-CoA, is palmitic acid, In the presence of 30 mu M methylmalonyl-CoA, microsomes or cytosol incubate d with [C-14]malonyl-CoA, or [H-3]acetyl-CoA, synthesize a fatty acid eluting in the position corresponding to a branched fatty acid of 14 c arbon in the straight chain backbone, in addition to palmitic acid. Co pyright (C) 1996 Elsevier Science Ltd.