title: Involvement of cytochrome P-450 enzyme activity in the selectivity and safening action of pyrazosulfuron-ethyl.
abstract: To investigate the selectivity and safening action of the sulfonylurea herbicide pyrazosulfuron-ethyl (PSE), pyrazosulfuron-ethyl O-demethylase (PSEOD) activity involving oxidative metabolism by cytochrome P-450 was studied in rice (Oryza sativa L cv Nipponbare) and Cyperus serotinus Rottb. Cytochrome P-450-dependent activity was demonstrated by the use of the inducers 1,8-naphthalic anhydride and ethanol, the herbicides PSE, bensulfuron-methyl, dimepiperate and dymron, or the inhibitor piperonyl butoxide (PBO). Growth inhibition in C serotinus seedlings was more severe than that in rice seedlings. O-Dealkylation activities of PSE were induced differently in rice and in C serotinus, with distinctly higher activity in rice seedlings. The induced PSEOD activities were slightly inhibited by PBO in rice seedlings, whereas they were strongly inhibited in C serotinus seedlings. Dimepiperate and dymron were effective safeners of rice against PSE treatment. Treatments with herbicide alone resulted in less induction of PSEOD activity compared with combined treatments of the herbicide and safener. PSEOD activity in rice seedlings induced with herbicide alone was strongly inhibited by PBO, whereas it was weakly inhibited in rice seedlings induced with combinations of PSE and two safeners. These results suggest that O-demethylation by cytochrome P-450 enzymes may be involved in the metabolism of PSE and may contribute to its selectivity and safening action. Furthermore, these results suggest the existence of a multiple form of cytochrome P-450 in plants.
authors.affiliation: Upland Weed Laboratory, Department of Farmland Utilization, National Agriculture Research Center, 3-1-1 Kannondai, Tsukuba City, Ibaraki Prefecture, 305-8666 Japan.
authors.forename: M S
authors.initials: MS
authors.lastname: Yun
authors.forename: I S
authors.initials: IS
authors.lastname: Shim
authors.forename: K
authors.initials: K
authors.lastname: Usui
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects* / Q000378:metabolism; D004790:Enzyme Induction; D006540:Herbicides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D019684:Magnoliopsida / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D008861:Microsomes / Q000201:enzymology; D012275:Oryza / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development; D010090:Oxidoreductases, O-Demethylating / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010574:Pesticide Synergists / Q000494:pharmacology; D010671:Phenylurea Compounds / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010882:Piperonyl Butoxide / Q000494:pharmacology; D010940:Plant Proteins; D011720:Pyrazoles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011743:Pyrimidines / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D013045:Species Specificity; D013453:Sulfonylurea Compounds
chemical_list: C492368:1-(alpha,apha-dimethylbenzyl)-3-(4-methylphenyl)urea; D006540:Herbicides; D010574:Pesticide Synergists; D010671:Phenylurea Compounds; D010940:Plant Proteins; D011720:Pyrazoles; D011743:Pyrimidines; D013453:Sulfonylurea Compounds; C433343:ethyl 5-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-1-methylpyrazole-4-carboxylate; D003577:Cytochrome P-450 Enzyme System; D010090:Oxidoreductases, O-Demethylating; D010882:Piperonyl Butoxide