CYTOCHROMES-P450 FROM PAPILIO-POLYXENES - ADAPTATIONS TO HOST-PLANT ALLELOCHEMICALS

1. Papilio polyxenes, a caterpillar which feeds on xanthotoxin-contain ing plants, has cytochromes P450 that are six- to 100-fold less sensit ive to the suicide substrate inhibitor, xanthotoxin. than cytochromes P450 from Manduca sexta, which does not survive on xanthotoxin-contain ing plants. 2. Xanthotoxin is a suicide substrate inhibitor of O-demet hylation of p-nitroanisole by M. sexta microsomes but a reversible inh ibitor of O-demethylation by P. polyxenes microsomes. 3. Aldrin epoxid ation is irreversibly inhibited by xanthotoxin in both species. 4. Pat terns of cross inhibition demonstrate that O-demethylase and aldrin ep oxidase from both species and the P. polyxenes xanthotoxin-metabolizin g cytochrome P450 are distinct enzymes.