COMPARISON OF DROSOPHILA CYTOCHROME-P450 METABOLISM OF NATURAL AND MODEL SUBSTRATES

Metabolism of some insecticides and toxic natural plant compounds is k nown to involve cytochrome P450 enzymes. Correlations between insectic ide resistance and deethylation of the model substrate, 7-ethoxycoumar in, have prompted its use in screens for potentially resistant insect populations, The applicability of this model substrate as an indicator of the enzyme activities and inductive responsiveness of cytochrome P 450 isoforms involved in the metabolism of carnegine was investigated. This toxic isoquinoline alkaloid is found in the host-plants of some species of cactophilic Drosophila. The results show that the ethoxycou marin (ECOD) assay does not accurately predict carnegine metabolism ei ther quantitatively or with respect to the overall pattern of activity . Therefore, the ECOD assay may be as isozyme-specific in insects as h as already been demonstrated in mammals and its use as an indicator of general P450 activity is questionable. (C) 1997 Elsevier Science Ltd. All rights reserved.