Fatty Acid Synthesis in Aquatic Animals and Its Metabolism in Carp, Cyprinus cardo

Abstract

Lipid metabolism and its regulation in aquatic organisms seed to differ considerably from those in mammals. In our experiments, carp starved for 10 days or fed fat-free diet for 35 days had almost the same hepatopancreas acetyl CoA carboxylase (ACC) specific activity levels as the controls. On supplementing the fat-free diets with 5% fatty acid, there was no depression of the specific activity of carp hepatopancreas ACC. The administration of a fat-free diet for 35 days resulted in increased specific activity of hepatopancreas fatty acid synthetase (FAS) and supplementing it of with 5% fatty acid decreased the specific activity of carp hepatopancreas FAS. An injection insulin or alloxan had no effect on the specific activity of carp hepatophacreas ACC or FAS. The activation of ACC from aquatic organisms required citrate and Mg2+ and that of FAS required NADPH, as is also the case in mammals. In carp hepatopancreas, the specific activity of ACC was 45mol/min/mg protein and that of FAS, 421pmol/min/mg protein. Both these values are low compared to those in mammals. In another aquatic 7 species tested, the specific activity of lipogenic enzymes was about one tenth that in carp hepatopancreas though crude enzymes prepared from whole body were examined. The present data indicate that lipogenesis in fish, and other aquatic organisms is apparently in a reduced state.