Proteolytic profile in the larval midgut of Chilo suppressalis Walker (Lepidoptera: Crambidae)

Chilo suppressalis is a key constraint on production of rice. The current research was conducted to study the types of digestive proteases in the larval midgut of C. suppressalis. It was found that activity of total digestive proteases increased from the first to the fifth larval instars, which showed different nutritional requirements. Four types of proteinases and two types of exopeptidase were identified so that their activities from the highest to the lowest activities is trypsin‐like, chymotrypsin‐like and elastase for proteinases, and amino and carboxypeptidases for exopeptidases. Meanwhile, just one type of cysteine protease, cathepsin D, was determined in the fourth and fifth instar larvae. The optimal pH for activity of total protease was found to be pH 9–10 and optimal temperature was observed to be 35–40°C, where there was the highest proteolytic activity. Some specific inhibitors of proteases including PMSF, TLCK, TPCK, DTT, E‐64, cystatin, phenanthroline and EDTA were used to confirm the types of proteases in the midgut of C. suppressalis.