The Intracellular Distribution of Enzymes of Carbohydrate Degradation in the Fat Body of the Adult Male Cockroach

-The intracellular distribution and maximal activities of phosphorylase, trehalase, all the enzymes of glycolysis, NAD and FAD-linked glycerol 3-phosphate dehydrogenase, arginine kinase, and adenylate kinase have been determined in the fat body of the adult male cockroach Periplaneta americana. Phosphorylase activity is predominantly in the soluble form but some can be sedimented. Both forms of the enzyme exhibit large increases in activity due to the presence of AMP. Only low activities of trehalase are detected and the enzyme appears to exist in both active and inactive forms. FAD-linked glycerol 3-phosphate dehydrogenase is only found in the mitochondria whereas the NADlinked enzyme and the glycolytic enzymes are located entirely in the cytosol. Of the glycolytic enzymes, phosphoglucomutase, phosphofructokinase and aldolase exhibit unusually low activities. The results suggest that conversion of hexose to triosc phosphate may occur predominantly via the pentose phosphate pathway and not via glycolysis. Whereas considerable activities of both types of glycerol-3-phosphate dehydrogenase are present in the fat body only low activities of lactate dehydrogenase are detected in the tissue. I N T R O D U C T I O N WORK with whole insects and tissues from a variety of insects has established that the glycolytic pathway functions in insects (KILaY, 1963; CHERFURKA, 1965; SACKTOR, 1965, 1970). Studies, in recent years, on glycogen breakdown and glycolysis in flight muscle have led to a reasonable understanding of changes in such processes and their control during flight (CRABTREE and NEWSHOLME, 1975; SACKTOR, 1975). Unfortunately, no such comprehensive and detailed study of glycogenolysis and glycolysis has been carried out on the fat body of any one insect despite the central r61e played by this tissue in insect metabolism (BAILEY, 1975). As part of a wider study of fat body intermediary metabolism and its control, we now report an investigation of the intracellular distribution and maximal activities of enzymes of carbohydrate degraclarion in the adult male cockroach, Periplaneta americana. MATERIALS AND M E T H O D S