Enzyme activities involved in lipid metabolism during embryonic development of Macrobrachium borellii

The activities of the enzymatic systems involved in the activation and degr adation of fatty acids, and in the synthesis of triacylglycerols and phosph olipids were studied in vitro using total cellular homogenate and subcellul ar fractions of eggs of the shrimp Macrobrachium borellii at different deve loping stages. Egg development was divided into seven stages based on morph ological features of the embryo. Palmitoyl-CoA ligase activity increased as the embryo developed and showed its maximum at stage V. An increase in the synthesis of triacylglycerols and diacylglycerols was also observed at thi s stage. Diacylglycerylethers were synthesized more actively during the fir st stages of development. The higher specific activity observed in total ho mogenate than in microsomal fraction suggested that their synthesis was not exclusively microsomal. Phospholipid synthesis was very active all along d evelopment, reflecting active membrane biosynthesis. The highest activity o f the cytosolic triacylglycerol lipase was observed at stage V. Fatty acid degradation, measured as mitochondrial beta-oxidation activity, did not var y significantly during development. We conclude that both the anabolic and catabolic processes concerning lipid metabolism are very active, with value s similar to those described for adult hepatopancreas, revealing the major role of lipids during shrimp embryogenesis energetics, and that the highest activities of lipid synthesis-hydrolysis take place at stage V when embryo s are under active organogenesis. (C) 2000 Wiley-Liss, Inc.