除草剂靶酶—AHAS酶及基因突变体与除草剂设计(Ⅱ).AHAS及W464突变酶与除草活性分子的相互作用

Studies on Herbicide Design through Mutation on Herbicidal Target Acetohydroxyacid Synthase(Ⅱ).Effects of mutagenesis at tryptophan 464 of Escherichia coli acetohydroxyacid synthase Ⅱ on herbicidal molecules

乙酰羟基酸合成酶(AHAS)是磺酰脲类、咪唑啉酮类、三唑嘧啶磺酰胺类及水杨酸类除草剂的作用靶标,大田使用中杂草对这几类除草剂产生抗性的主要因素是AHAS酶的突变.利用大肠杆菌AHASⅡ中464位的色氨酸突变体(W464A、W464F、W464L、W464Y),研究了野生型和突变酶对商品化除草剂(氯嘧磺隆、氯磺隆、咪唑乙烟酸、咪唑喹啉酸)以及烷硫基磺酰脲的敏感性.野生型E.coli AHASⅡ对这些化合物的抑制作用较为敏感,而突变酶对其呈现出不同程度的抗性,使商品化除草剂的抑制常数增加了10～1.0×104倍不等,烷硫基磺酰脲的抑制常数增加幅度较小.烷硫基磺酰脲1a对W464L突变酶的高抑制活性,暗示着发展针对靶酶抗性的除草剂的可能性.

Acetohydroxyacid synthase （AHAS） is a target for sulfonylurea and imidazolinone herbicides. Resistance to sulfonylurea and imidazolinone herbicides can occur by mutation in AHAS. Four E. coli AHAS Ⅱ mutants （W464A, W464F, W464L, W464Y） and wild type were characterized for the sensitivities to commercial inhibitors （chlorimuron ethyl, chlorsulfuron, imazethapyr, imazaquin） and some newly synthesized alkylthio-containing sulfonylureas. Wild type enzyme showed it was sensitive to these herbicidal compounds. The mutants showed they were resistant to the commercial sulfonylureas with the increases of Ki^app values from dozens to several thousand fold. Substantial differences were observed in the sensitivity of wild type and mutant enzymes to these various inhibitors. Alkylthiocontaining sulfonylureas seem they met relatively weak resistance by W464 mutant enzymes.