Genetics of xenobiotic metabolism in Drosophila. I. Genetic and environmental factors affecting glutathione-S-transferase in larvae.

The enzyme glutathione-S-transferase, which plays a crucial role in xenobiotic detoxification, was investigated in Drosophila melanogaster. Based upon examination of substrate specificities and pH optima, it was observed that the enzyme in Drosophila is considerably more restricted in its activities than in mammals. The effects of various xenobiotics on activities in third instar larvae were examined. While beta-naphthoflavone and phenobarbital had no effect, pentamethyl benzene (PMB) administration resulted in a 50% increase in enzyme activity. Comparison of lines of known genetic composition indicates that the degree of response to PMB is modulated by genes on chromosome II, and that differences exist with respect to the patterns of response of activities towards the substrates 1-chloro-2, 4-dinitrobenzene and ethacrynic acid. Results obtained suggest the existence of at least two loci on chromosome II that code for glutathione S-transferase isozymes.