C . cephalonica is a moth widely distributed in tropical and temperate regions of the world. It infests a variety of products including grains, seeds, cereal products, peas, beans, coffee and tobacco. The identification and characterization of proteases from insect midgut are important in developing cultivars resistant to insect attack. In this study, proteolytic activities in the larval midgut of C. cephalonica were investigated. Proteinases were obtained from the midguts of fourth-instar larvae. The insects were cold immobilized, dissected, and the midguts were surgically removed from the larvae and placed in iso-osmotic saline. Midgut tissue homogenates were centrifuged at 15,000 g for 10 min at 4º C and the supernatants were used as enzymes sources. The midgut proteinases were able to hydrolyze the substrates, L-BapNA and azocasein. The maximum proteolytic activities were observed at different PHs. In both substrates, ph optimum was of 10. L-BApNA was utilized to investigate the midgut activity in the presence of different protease inhibitors. It was observed that, soybean inhibitors (Bowman Birk and Kunitz), benzamidine, TLCK, were able to inhibit midgut proteinases. Some inhibition by TPCK was detected. The optima temperature for enzymatic assays was 40º C, using BApNA as substrate. The effects of Ca²⁺ and Mg²⁺ (10 mM) on midgut proteolytic activities were also investigated. These divalent cations did not affect BApNa hydrolysis. These data suggest that protein digestion in C. cephalonica is primarily dependent of trypsin-like proteinases.

Supp.: FINEP, FUNDECT, CNPq.