Proteolytic compartmentalization and activity in the midgut of Andrallus spinidens Fabricius (Hemiptera: Pentatomidae)

Digestive proteolytic activity in the alimentary canal of Andrallus spinidens, a potential biocontrol agent of lepidopteran larvae, was studied by considering enzyme compartmentalization and diversity. The alimentary canal of adults consists of a foregut, a four- sectioned midgut, namely V₁ to V₄ (ventriculus), and a hindgut. The optimal pH for general proteolytic activity was found to be at pH 8 with a small peak at pH 6. Results revealed that there are several specific proteases in the midgut of A. spinidens, including trypsin-like, chymotrypsin-like, and elastase as serine proteases, and cathepsins B, L and D as cysteine proteases, in addition to two exopeptidases of carboxy- and aminopetidases. Compartmentalization of digestive proteolytic activity showed that V₃ is the main area of proteolytic secretion for both general and specific proteases and that V₄ has the lowest enzymatic role, so that four out of the eight specific proteases found showed no activity in this section. The lowest and the highest proteolytic activity was found to be in the 1^st and 4^th nymphal instars, respectively. Using the specific inhibitors phenylmethylsulfonyl fluoride, Na-p-tosyl-L-lysine chloromethyl ketone, Ntosyl- L-phenylalanine chloromethyl ketone, L-trans-epoxysuccinyl-leucylamido-( 4-guanidino)-butane, cystatin, phenanthroline and ethylendiamidetetraacetic acid, we verified the presence of all specific proteases noted using both biochemical assays and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Our findings demonstrated that A. spinidens could utilize several caterpillars because of the presence of various of proteases in its midgut.