Oxidative Metabolism of Chlorotoluron in Wheat Cell Cultures: Intervention of Cytochrome P-450 Monooxygenases
Metabolisme oxydatif du chlorotoluron chez des cultures cellulaires de ble : Intervention de monooxygenases a cytochrome P-450
Résumé
The enzyme systems responsible for the oxidative metabolism of a herbicide, chlortoluron, have been investigated in microsomes isolated from wheat cell cultures, which also contain good levels of cinnamate 4-hydroxylase and laurate hydroxylase activities. Chlortoluron is oxidized to a hydroxyl derivative on the methyl of the aromatic ring and to an n-monodemethyl derivative. Both enzymatic activities possess the characteristic properties of cytochrome p-450 monoxygenases (cellular localization, co-factor requirements, sensitivity to known inhibitors of cytochrome p-450 monooxygenases). The four activities measured (cinnamate 4-hydroxylase, laurate hydroxylase, chlortoluron hydroxylase n-demethylase) and the levels of cytochrome p-450 are increased after treatment of the cells with various compounds (herbicides, fungicides and herbicide antidotes). Qsar studies have shown that structural analogues of chlortoluron alter the metabolism of the latter. Taken together, these data suggest that cytochrome p-450 monooxygenases are involved in the hydroxylation and n-demethylation reactions of the herbicide. The characteristics of the two activities suggest that separate enzymes catalyze each of the two reactions.
Les systemes enzymatiques responsables du metabolisme oxydatif d'un herbicide, le chlortoluron, ont ete etudies dans des microsomes isoles de cultures cellulaires de ble, qui renferment egalement de bons niveaux d'activites cinnamate 4-hydroxylase et laurate hydroxylase. Le chlortoluron est oxyde en un derive hydroxyle sur le methyle du cycle aromatique et en un derive n-monodemethyle. Les deux activites enzymatiques possedent les proprietes caracteristiques des monoxygenases a cytochromes p-450 (localisation cellulaire, besoins en co-facteurs, sensibilite a des inhibiteurs connus de monooxygenases a cytochrome p-450). Les quatre activites mesurees (cinnamate 4-hydroxylase, laurate hydroxylase, hydroxylase n-demethylase du chlortoluron) et les teneurs en cytochrome p-450 sont augmentees apres des traitements des cellules par des composes varies (herbicides, fongicides et antidotes d'herbicides). Des etudes qsar ont montre que des analogues structuraux du chlortoluron modifient le metabolisme de celui-ci. Prises dans leur ensemble, ces donnees suggerent que des monooxygenases a cytochrome p-450 sont impliquees dans les reactions d'hydroxylation et de n-demethylation de l'herbicide. Les caracteristiques des deux activites laissent penser que des enzymes distinctes catalysent chacune des deux reactions
Domaines
Sciences du Vivant [q-bio]
Origine : Fichiers produits par l'(les) auteur(s)