Toxin-binding properties of cytochrome P450 in Saccharomyces cerevisiae and Kluyveromyces marxianus

Microsomes from Kluyveromyces marxianus GK1005 examined by carbon monoxide difference spectroscopy showed no evidence of cytochrome P450, in contrast to microsomes isolated from a control strain of Saccharomyces cerevisiae. Benzo[a]pyrene produced a typical Type I-binding spectrum with microsomes of both yeasts, with K-s values of 82 mu M (S. cerevisiae) and 70 mu M (K. marxianus). While aflatoxin B-1 generated a typical Type I-binding spectrum with microsomes from S. cerevisiae (K-s of 178 mu M), the toxin did not produce a recognisable binding spectrum with microsomes from K. marxianus.