Lipase Enzyme Activity in Digestive System of Helicoverpa armigera Hb. (Lep.: Noctuidae) and Effect of Some Laboratory Compounds on It

Cotton boll worm "Helicoverpa armigera" is one of the most important pests in cultivated crops. Physiological understanding is one of the basic steps to control pests by chemicals and pathogens. In this study, Lipase enzyme characteristics in mid gut of cotton boll worm were studied. Studying of enzyme activity and other treatments were done by Auto analyzer and chromogenic method. The highest and langest enzyme activity were observed in the 6th instar larvae and male adults, respectively, The highest enzyme activity was observed at 40°C. Optimum pH for lipase enzyme activity in the mid gut was 9.5. After eight week enzyme activity at -20°C was 17% of its activity in the first week. While enzyme activity at 4°C after five weeks, was 6% of its activity in the first week, then enzyme activity completely stopped. The results of the study of enzyme activity at different times of starvation showed that enzyme activity after four day starvation was reduced to approximately 9% of its activity when larvae had fed. Enzyme activity was decreased by ethanol 96%, and 3, 4 and 5mM of NaCl and 3, 4 and 5mM of CaCl2 and different concentrations of SDS. Enzyme activity was increased by 1 and 2mM of NaCl and 5mM of KH2PO4. Different concentrations of Tris, EDTA concentration up to 25% ethanol and 4mM of KH2PO4 also had no observed effect on enzyme activity.