Identification and characterization of hydrolytic enzymes from the midgut of the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Midgut hydrolytic enzymes of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) were identified and partially characterized. Km, Vmax, optimum pH, and specific activity were determined for proteolytic enzymes and αamylases. All hydrolytic enzyme activity had an optimum pH value in the alkaline pH range. We observed major serine protease activity, together with minor cysteine-like activity, the former being significantly inhibited by soybean trypsin inhibitor (SBTI) and aprotinin. Moreover, different degrees of inhibition were observed with synthetic protease inhibitors. Electrophoretic methods revealed 3 isozymes of α-amylases, of which 2 had higher molecular weight and were more active than the other. Inhibition of amylolytic activity was observed with wheat α-amylase inhibitor (WAAI), whereas partially purified maize, chickpea, and bean seed crude extracts did not exhibit inhibitory activity toward α-amylases. To the best of our knowledge this is the first report on the properties of α-amylases from Helicoverpa armigera and the effects of several plant-originated a-amylase inhibitors on them.