NSC-161128

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.

INDIVIDUAL differences in taste sensitivity to phenyl thiocarbamate in human populations, first demonstrated in 1931, were soon shown to be due to segregation at a single autosomal locus1. Although this phenomenon was initially very interesting, its dependence on a synthetic compound relegated it to a laboratory demonstration of single locus determination of perceptual differences. More recent work concerning the antithyroid activity of PTC and similar compounds in several naturally occurring foodstuffs, however, has prompted renewed interest in this phenomenon2.