Characterization of 7-ethoxycoumarin-O-deethylase from malathion resistant and susceptible strains of Drosophila melanogaster |
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| Affiliation: | 1. Plant Protection Department, Faculty of Agriculture, Assiut University, Assiut 71526, Egypt;2. Center for Health and the Environment, University of California Davis, CA 95616, USA;3. Department of Environmental Toxicology, University of California Davis, CA 95616, USA;2. School of Chemistry, The University of Melbourne, Parkville, Victoria, Australia;3. Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria, Australia |
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| Abstract: | Mixed-function oxidase activity in a D. melanogaster strain carrying at least two closely linked malathion resistance genes on chromosome 3 was compared with the susceptible Canton S strain. The kinetics of O-deethylation of 7-ethoxycoumarin (7-ECD activity) with respect to pH, temperature, substrate and cofactor (NADPH) affinities and the response to metal salts of both strains were similar. The resistant strain had approx. 5-fold greater 7-ECD specific activity, and a parallel increase in total cytochrome P-450 content. Developmental stage, sex and nutritional state affected Drosophila 7-ECD activity. The intestine, fat body and Malpighian tubules contained the largest 7-ECD specific activity. Both susceptible and resistant strains had similar patterns of 7-ECD expression and differed only in total activity. In addition to more cytochrome P-450, the resistant strain had increased amounts of two microsomal, heme-staining polypeptides (Mr = 50 and 54 K after SDS-PAGE). The results suggest that the genetic change in the resistant strain involves the regulation of the Drosophila cytochrome P-450 system. |
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