Occurrence of cytochrome P-450 mono-oxygenases in the metabolism of chlorotoluron by wheat microsomes
Résumé
In previous studies, it has been shown that wheat cell cultures actively metabolize chlorotoluron (CPU). That metabolism was found sensitive to several cytochrome P45 inhibitors, and could be stimulated by treatments of cell cuitures with compounds such as cyometrinil, dichlormid and 2,4-D(l,2). Mono-oxygenases implicated in the metabolism of CPU were then studied in microsomal preparations from wheat cell cultures pretreated with cyometrinil.
Non-chlorophyllous cells of wheat (Triticum aestivum var. Koga 11) were routinely cultivated as previously described(2). At the beginning of experiments, 4-8 day-old suspensions were subcultured at an inoculum density of 4 mg dry wt ml. After 4 days of growth, cells were put in fresh culture medium containing 400 µM cyometrinil. Microsomes were isolated 3 days later. Oxygenase activities were tested using 100,000 g pellets, referred ·to· as microsomal fractions. Protein concentrations In these fractions were 2-4 mg/ml. Reaction mixtures, adjusted to a final volume of 200 µl with 0.1 M (pH 7.5) potassium buffer, usually contained 16.6 µBq of 1 4C-CPU plus cold herbicide to a final concentration of 500 µM, 1 mM NADPH, a NADPH regenerating system and 0.25 - 0.40 mg of microsomal proteins. Enzymatic reactions were stopped after 30 min with 20 µl of 4N HCl. Rates of cinnamate hydroxylase and laurate hydroxylase activities were assessed in similar conditions for comparison…
Domaines
Sciences du Vivant [q-bio]
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