Proteolytic activity in the midgut of the crimson speckled moth Utethesia pulchella L. (lepidoptera: arctiidae)

Samples were prepared from the midgut of 4th instar larvae of the crimson speckled moth Utethesia pulchella L. to find proteolytic activity and properties. Result revealed the presence of high proteolytic activity in the midgut when taking into account specific proteinases including trypsin-like, chymotrypsin-like, elastase and two exopeptidase (aminopeptidase and carboxipeptidase). The optimal pH of general protease was 8 and 7 when using azocasein and hemoglobin as general substrates, respectively. The optimal temperature of the total proteolytic activity in the midgut of U. pulchella was 25°C and 30°C when using azocasein and hemoglobin, respectively. Proteolytic activity was inhibited significantly by soybean trypsin inhibitor (SBTI), phenylmethylsulfonyl fluoride (PMSF), trypsin inhibitor (TLCK), chymotrypsin inhibitor (TPCK) and Phenanthroline. These results provide evidences for the presence of serine proteinases as the major proteases in the midgut of U. pulchella; a key rangeland pest in warm climates. The interaction between digestive proteases and protease inhibitors have potentially important consequences for pest management programs.