Among lipids, triacylglycerol (TAG) is a major component of the insect diet and the midgut is the main site for its digestion, absorption and processing. We have shown that in larval Manduca sexta, which is widely used as insect model, dietary TAG is hydrolyzed in the lumen to fatty acids (FAs) and glycerol. FAs are absorbed efficiently and once into the midgut cell, they are transformed to diacylglycerol (DAG) by the phosphatidic acid pathway. We have also shown that in the enterocyte, DAG is converted to TAG, which ultimately serves as a reservoir from which sn-1,2-DAG are exported to the hemolymph. In order to elucidate the events of lipolysis that take place in the midgut, we have partially characterized a triacylglycerol lipase from the midgut of larval M. sexta. Activity of the lipase from the midgut of larval M. sexta (L-Mg) was identified and measured using [ 3 H]-trioleoylglycerol as a substrate. The enzyme showed a cytosolic subcellular localization and catalyzed the hydrolysis of TAG, DAG and monoacylglycerol (MAG), but showed highest affinity for TAG and DAG. L-Mg exhibited an optimum activity at pH of 8.3 and was not affected by high concentrations of NaCl. The stereospecific analysis of the end products of TAG hydrolysis were assayed using trioleoyl-[3 H]-glycerol and two NaCl concentrations, 150 and 500 mM. Unlike the in vitro activity of fat body lipase, which led to accumulation of MAG, in the both conditions assayed the

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