Identification and partial characterization of digestive proteinases from two species of bedbug (Hemiptera: Cimicidae)

The digestive midgut of Cimex hemipterus (Fabr.) and Cimex lectularius L. contains cathepsin B, aminopeptidase, and an acidic proteinase that hydrolyzes haemoglobin at an optimal pH of 3.4. Cathepsin B was demonstrated by hydrolysis of benzoyl-DL-arginine-β-napthylamine at an optimal pH of 5.4. Hydrolysis of the substrate was activated by thiol chemicals and EDTA and inhibited by iodoacetamide (IAA) and horse serum. Maximum aminopeptidasehydrolysis of leucine-p-nitroanilide occurred at pH 8.4. Aminopeptidase activity was activated by MgCl2 and inhibited by EDTA, thiol chemicals, and CaCl2. Only C. hemipterus aminopeptidase was inhibited by IAA. The digestive proteinases in bedbugs are similar to those reported for other blood-sucking hemipteran insects.