Purification and characterization of a digestive lipase in Eurygaster integriceps Puton (Hemiptera: Scutelleridae)

Wheat grains contain 8-13% of lipid in their germplast which places on molecular surface of starch increasing flour quality. Insects depend on digestive enzymes to utilize food resources. There are few studies on digestive lipases of insects with significant contribution of lipids in food molecules. In this study, a digestive lipase of Eurygaster integriceps, which is the major pest of wheat in Iran, was purified and characterized. Purification process revealed an enzyme with molecular weight of 25.4 kDa, recovery of 19.58, purification fold of 69.70 and specific activity of 2.37 micromol/min/mg protein. Optimal pH and temperature experiments showed the highest enzymatic activity at 6 and 25 ºC, respectively. Enzyme incubation in these values revealed enzymatic stability for 1-3 hours. Different concentrations of EDTA had no effects on the enzymatic activity but PMSF significantly decreased it. Analysis of the enzymatic kinetic parameters showed mixed inhibition of PMSF on the purified lipase of the Sunn pest. Study on insect lipases is important due to their role in hydrolysis of proteinaceous inhibitors in transgenic plants so it may open a sustainable pest management via transgenic plants.