A PLANT METABOLIC-ACTIVATION SYSTEM FROM PERSEA-AMERICANA WITH CYTOCHROME P450-DEPENDENT AND PEROXIDASE-ACTIVITIES

Microsomal fractions from different tissues of various plants (potato, cauliflower, aubergine, avocado pear, courgette, cucumber, banana, ki wi and strawberry) were prepared and their content of cytochrome P-450 (cyt-P450) determined. A S117 fraction from Persea americana (avocado pear) presented the highest content of cyt-P450. As a consequence of these data, we have developed and characterized this fraction as a pla nt metabolic activation system. The P. americana S117, used in this wo rk, contains 0.75 +/- 0.04 mg of protein per ml, 0.788 +/- 0.078 nmol of cyt-P450 per mg of protein and has a peroxidase activity of 0.036 /- 0.005 (nmol tetraguaiacol/mu g protein/min). The P. americana cyt-P 450 remained stable during at least 60 days, stored at - 80 degrees C. This fraction activated 2-aminofluorene to a mutagenic product in S. typhimurium TA98, while it had no effect on the benzo[a]pyrene activat ion. The treatment of the P. americana S117 with CO, the addition of d iethyldithiocarbamate (DETC) or the absence of a NADPH-generating syst em in the activation mix, produced a partial inhibition of the 2-amino fluorene activation. Both peroxidase activity and a cyt-P450-dependent activity are assumed to be involved in the activation of this chemica l mediated by P. americana S117.