ACTIVATION OF PROPHENOLOXIDASE WITH 2-PROPANOL AND OTHER ORGANIC-COMPOUNDS IN DROSOPHILA-MELANOGASTER

Activation with 2-propanol and other organic compounds of prophenoloxi dase purified from pupae of Drosophila melanogaster was analyzed. A1, one of the two isozymes of the prophenoloxidase, could be activated wi th both an endogenous activating system and artificial organic compoun ds including alcohols. A1 was activated within 2 min after addition of 2-propanol. The phenoloxidase activity of A1, which had been activate d with 2-propanol, decreased gradually by lowering the concentration o f 2-propanol taking c 60 min to attain a low level, and the activity c ould be re-elevated at the re-introduction of 2-propanol. Thus the rev ersibility of the activation of A1 in response to the change of the co ncentration 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-degrees-C and optimum pH was 7.5. The fi nal level of the phenoloxidase activity, which had been activated with 2-propanol, was higher than that activated with the endogenous activa ting system. The activated state of A1 showed properties of a tyrosina se-type phenoloxidase. The results suggested that the activation of A1 with 2-propanol is caused by the reversible conformational change of the prophenoloxidase molecule.