PROTEASE-MEDIATED PROPHENOLOXIDASE ACTIVATION IN THE HEMOLYMPH OF AMERICAN COCKROACH PERIPLANETA-AMERICANA

Prophenoloxidase has been successfully obtained from the haemolymph of the cockroach Peviplaneta americana using cane sugar saline solution, The proenzyme was activated by various exogenously added proteases su ch as chymotrypsin, trypsin, subtilisin and thermolysin. Thermolysin w as found to be the greatest activator, followed by chymotrypsin and su btilisin. Chymotrypsin activation showed a lag period when compared wi th the other proteases tested, indicating that activation by chymotryp sin followed an indirect path, whereas, subtilisin and thermolysin act ivated the proenzyme directly. Exogenously added protease inhibitor sh owed inhibition towards protease-mediated prophenoloxidase activation, Benzamidine inhibited chymotrypsin and trypsin activation, whereas so ybean trypsin inhibitor inhibited trypsin, In situ inhibitor isolated from the haemocytes of Periplaneta americana inhibited the prophenolox idase activation and showed evidence for the presence of a built-in in hibition system for the release of the components of the prophenoloxid ase activating system of P. americana, Electrophoretic localization of activated phenoloxidase showed two bands, suggesting the dimeric cond ition of high mel. wt prophenoloxidase.