Activation of long chain fatty acids by subcellular fractions of rat liver: I. Activation oftrans-unsaturated acids

The optimal fatty acid to protein ratio for maximum rat liver microsomal or mitochondrial activation of thetrans-monounsaturated acids elaidate ortrans-vaccenate is similar to the ratio for maximum palmitate activation but approximately double the optimal ratio for maximum activation of thecis-unsaturated fatty acids, oleate,cis-vaccenate, or of thetrans-diunsaturated linelaidic acid. However, when the substrate is a fatty acid-albumin complex rather than free fatty acids, optimal fatty acid activation appears to be independent of geometrical configuration or degree of unsaturation. All-trans retinoate, d-α-tocopheryl acid succinate, and dihomogeranoate are not activated themselves, but at low concentrations extensively inhibit activation ofcis-acids (oleate,cis-vaccenate, petroselenate, linoleate, linolenate, arachidonate) and thetrans-diunsaturated linelaidate but do not affect activation of palmitate ortrans-monounsaturated acids elaidate andtrans-vaccenate. Anionic, cationic or nonionic detergents in a pH 7.4 buffered incubation medium were shown to inhibit, have no effect on, or apparently activate oleate activation, respectively, while not affecting or inhibiting palmitate and elaidate activation. The effect observed was dependent on the fatty acid to protein ratio, the fatty acid configuration and the detergent concentration.