CYTOCHROME-P450 IN TRYPANOSOMATIDS

Post-mitochondrial supernatant extracts prepared from bloodstream form s of Trypanosoma brucei brucei, T. cruzi epimastigotes, Leishmania don ovani promastigotes and Crithidia fasciculata have been found to catal yse cytochrome P450-dependent reactions. Appreciable ethoxycoumarin de ethylase and ethoxyresorufin deethylase activities were found in all o f the above trypanosomatids, with T. cruzi epimastigotes having the hi ghest activity (57.1 and 10.7 pmol/min/mg protein, respectively). In a ll four species these reactions were inhibited by the cytochrome P450 inhibitors carbon monoxide, proadifen and metyrapone. In contrast to r at liver microsomes, the trypanosomatid extracts showed no detectable pentoxyresorufin depentylase or pentamidine hydroxylase activity. Both C. fasciculata and T. b. brucei post-mitochondrial supernatants showe d carbon monoxide difference spectra consistent with the presence of c ytochrome P450 (9.6 and 6.3 pmol/mg protein, respectively). An additio nal hemoprotein which gave a carbon monoxide difference peak at 420 nm was also detected in C. fasciculata and T. b. brucei microsomes and C fasciculata mitochondria. Subcellular fractionation of both early and late log C. fasciculata showed that the ethoxycoumarin deethylase act ivity was enriched in the microsomal fraction.