Activation of prophenoloxidase with 2-propanol and other organic compounds in Drosophilamelanogaster

Abstract Activation with 2-propanol and other organic compounds of prophenoloxidase purified from pupae of Drosophila melanogaster was analyzed. A 1 , one of the two isozymes of the prophenoloxidase, could be activated with both an endogenous activating system and artificial organic compounds including alcohols. A 1 was activated within 2 min after addition of 2-propanol. The phenoloxidase activity of A 1 , which had been activated with 2-propanol, decreased gradually by lowering the concentration of 2-propanol taking c 60 min to attain a low level, and the activity could be re-elevated at the re-introduction of 2-propanol. Thus the reversibility of the activation of A 1 in response to the change of the concentration of 2-propanol in the activating mixture could be observed. Optimum concentration of 2-propanol for the rate of activation was 50%, optimum temperature was 30°C and optimum pH was 7.5. The final level of the phenoloxidase activity, which had been activated with 2-propanol, was higher than that activated with the endogenous activating system. The activated state of A 1 showed properties of a tyrosinase-type phenoloxidase. The results suggested that the activation of A 1 with 2-propanol is caused by the reversible conformational change of the prophenoloxidase molecule.