Hassan Nemat M, Nemat Alla Mamdouh M
Botany Department, Faculty of Science, Damietta University, PO 34517, New Damietta, Egypt.
Physiol Mol Biol Plants. 2020 Jul;26(7):1505-1518. doi: 10.1007/s12298-020-00812-3. Epub 2020 Jun 11.
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.
本研究旨在探究异丙隆对小麦中谷胱甘肽相关酶[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)和谷胱甘肽过氧化物酶(GPX)]的抑制动力学。将异丙隆施用于10日龄的幼苗，持续12天，导致地上部鲜重和干重、蛋白质、硫醇和谷胱甘肽(GSH)显著降低；然而，氧化型谷胱甘肽(GSSG)升高，而GSH/GSSG比值下降，同时γ-GCS、GS、GR、GST和GPX的活性受到显著抑制；这种影响具有时间依赖性。异丙隆对GPX的IC50和Ki值最低，对GST和GR均最高，对γ-GCS和GS均适中。除草剂显著降低了γ-GCS、GS和GPX的Vmax，但GST和GR的Vmax不变；然而，γ-GCS、GS、GST和GR的Km增加，而GPX的Km不变。每种酶体内和体外试验中Vmax、Km、Vmax/Km、kcat和kcat/Km变化的响应模式似乎最有可能相似。这些结果表明，异丙隆在小麦中诱导了防御系统的功能障碍，导致谷胱甘肽相关酶受到抑制，其中对GPX的抑制程度最明显，其次是γ-GCS、GS、GST和GR。这些发现可以得出结论，异丙隆竞争性抑制GST和GR；然而，对GPX的抑制是非竞争性的，对γ-GCS和GS的抑制是混合型的。
