The present study aimed at investigating the kinetic of inhibition of isoproturon to the GSH-associated enzymes [γ-glutamyl-cysteine synthetase (γ-GCS), glutathione synthetase (GS), glutathione reductase (GR), glutathione-S-transferase (GST) and glutathione peroxidase (GPX)] in wheat. Isoproturon, applied to 10-day-old seedlings for the following 12 days, provoked significant reductions in shoot fresh and dry weights, protein, thiols and glutathione (GSH); however, oxidized glutathione (GSSG) was elevated while GSH/GSSG ratio was declined with concomitant significant inhibitions in the activities of γ-GCS, GS, GR, GST and GPX; the effect was time dependent. IC50 and Ki values of isoproturon were lowest for GPX, highest for both GST and GR, and moderate for both γ-GCS and GS. The herbicide markedly decreased Vmax of γ-GCS, GS and GPX but unchanged that of GST and GR; however, Km of γ-GCS, GS, GST and GR increased but unchanged for GPX. The pattern of response of changing Vmax, Km, Vmax/Km, kcat and kcat/Km for in vivo and in vitro tests of each enzyme seemed most likely similar. These results indicate that a malfunction to defense system was induced in wheat by isoproturon resulting in inhibitions in GSH-associated enzymes, the magnitude of inhibition was most pronounced in GPX followed by γ-GCS, GS, GST, and GR. These findings could conclude that isoproturon competitively inhibited GST and GR; however, the inhibition was noncompetitive for GPX but mixed for both γ-GCS and GS.

中文翻译：

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小麦中谷胱甘肽相关酶对异丙隆的抑制动力学。

本研究旨在研究异丙基隆对GSH相关酶[γ-谷氨酰-半胱氨酸合成酶（γ-GCS），谷胱甘肽合成酶（GS），谷胱甘肽还原酶（GR），谷胱甘肽S-转移酶（GST）的抑制动力学。 ）和谷胱甘肽过氧化物酶（GPX）]。在接下来的12天中，将异丙隆用于10天大的幼苗，可显着降低枝条的鲜重和干重，蛋白质，硫醇和谷胱甘肽（GSH）；然而，氧化型谷胱甘肽（GSSG）却升高了，而谷胱甘肽/谷胱甘肽（GSSH）的比例却下降了，同时对γ-GCS，GS，GR，GST和GPX的活性也有明显的抑制作用。效果是时间依赖性的。异丙隆的IC50和Ki值对于GPX最低，对GST和GR最高，对γ-GCS和GS均中等。除草剂明显降低了γ-GCS的Vmax，GS和GPX，但GST和GR不变；但是，GPX的γ-GCS，GS，GST和GR的Km增加了，但没有变化。对于每种酶的体内和体外测试，改变Vmax，Km，Vmax / Km，kcat和kcat / Km的响应模式似乎很相似。这些结果表明，异丙基丙磺隆在小麦中诱导了防御系统的功能异常，导致了GSH相关酶的抑制，其中抑制程度在GPX中最为明显，其次是γ-GCS，GS，GST和GR。这些发现可以得出结论，异丙隆可以竞争性地抑制GST和GR。但是，抑制作用对GPX不具有竞争力，但对γ-GCS和GS却是混杂的。用于每种酶的体内和体外测试的kcat和kcat / Km似乎很相似。这些结果表明，异丙基丙磺隆在小麦中诱导了防御系统的功能异常，导致了GSH相关酶的抑制，其中抑制程度在GPX中最为明显，其次是γ-GCS，GS，GST和GR。这些发现可以得出结论，异丙隆可以竞争性地抑制GST和GR。但是，抑制作用对GPX不具有竞争力，但对γ-GCS和GS却是混杂的。用于每种酶的体内和体外测试的kcat和kcat / Km似乎很相似。这些结果表明，异丙基丙磺隆在小麦中诱导了防御系统的功能异常，导致了GSH相关酶的抑制，其中抑制程度在GPX中最为明显，其次是γ-GCS，GS，GST和GR。这些发现可以得出结论，异丙隆可以竞争性地抑制GST和GR。但是，抑制作用对GPX不具有竞争力，但对γ-GCS和GS却是混杂的。