Properties of phenoloxidases generated from prophenoloxidase with 2-propanol and the natural activator in Drosophila melanogaster.

Prophenoloxidases A1 and A3 in Drosophila melanogaster were activated with 2-propanol and a partially purified natural activator. For prophenoloxidase activation, the optimum temperature was 30 degrees C and the optimum pH was 8. Both mono- and diphenoloxidase activities were found in A1 and A3 activated with 2-propanol, whereas only diphenoloxidase activity was detected in A3 activated with a natural activator. The kinetic properties, Km and Vmax, were not similar in those phenoloxidases activated with different activating agents. The rate of inhibition of phenoloxidase by diethyldithiocarbamate and phenylthiocarbamate depended on the concentration of 2-propanol. Both compounds exhibited a noncompetitive pattern of inhibition.