Uptake of lipids by developing oocytes of the hawkmoth Manduca sexta. The possible role of lipoprotein lipase.

A plasma membrane preparation of Manduca sexta ovarian follicles was shown to contain lipoprotein lipase activity that hydrolyzes the diacylglycerol moiety of the hemolymph lipoprotein, lipophorin. Kinetic analysis demonstrated that low density lipophorin (LDLp) is a better substrate for the identified lipase activity than high density lipophorin (HDLp). The activity has a pH optimum of 9-9.5 and is partially inhibited by NaCl concentrations higher than 0.5 M. Diisopropylfluorophosphate (DFP) inhibits the membrane bound lipoprotein lipase activity completely and irreversibly. Incubation of follicle plasma membranes with [3H]-DFP radiolabels a 100-kDa membrane protein that may represent the lipoprotein lipase. The present results suggest that lipoprotein lipase activity may play an important role in the uptake of lipids by M. sexta oocytes.