Interaction between yeast cytochrome P-450 and chemical carcinogens

The binding of various chemical carcinogens to the glucose-inducible form of cytochrome (cyt.) P-450 in Saccharomyces cerevisiae was examined with reference to known metabolism in mammalian systems. All the carcinogens examined gave spectral interactions with the yeast cytochrome. The carcinogens benzo[a]pyrene and cyclophosphamide gave Type I binding, while benzidine and 2-naphthylamine gave Type II binding spectra indicating binding at the haem group. Dimethylnitrosamine gave undetectable binding in yeast microsomal fractions, but a Type I binding spectrum was seen with purified cyt. P-450 preparations. The demonstration that these carcinogens bind to yeast cyt. P-450 is discussed in the light of their genotoxicity.