Elskens M T, Penninckx M J
Laboratoire de Microbiologie de l'Université Libre de Bruxelles, Institut Pasteur, Belgium.
Eur J Biochem. 1995 Aug 1;231(3):667-72. doi: 10.1111/j.1432-1033.1995.tb20746.x.
Previous in vivo investigations have shown that glutathione reductase is one of the sites of action of the dithiocarbamate fungicide tetramethylthiuram disulphide (thiram) in the yeast Saccharomyces cerevisiae. The inactivation of glutathione reductase by thiram has now been demonstrated in vitro. This inactivation was time-dependent and occurred only with the enzyme in the reduced state and in the absence of glutathione. Since the turnover rate of the enzyme with thiram as a substrate was significantly higher than the rate of enzyme inactivation, it was suggested that more than one enzyme-inhibitor complex was involved in the reaction. Arguments supporting a covalent modification of glutathione reductase were further obtained by experiments carried out with [14C]thiram and gel filtration. A kinetic scheme for the inactivation is proposed and the relevance of the in vitro data to previous in vivo studies is discussed taking into consideration current concepts of glutathione reductase inactivation by affinity reagents.
先前的体内研究表明，谷胱甘肽还原酶是二硫代氨基甲酸盐类杀菌剂四甲基秋兰姆二硫化物（福美双）在酿酒酵母中的作用位点之一。现在已在体外证明福美双可使谷胱甘肽还原酶失活。这种失活是时间依赖性的，并且仅在还原态且不存在谷胱甘肽的酶中发生。由于以福美双为底物时酶的周转速率明显高于酶失活速率，因此表明反应中涉及不止一种酶 - 抑制剂复合物。通过用[14C]福美双进行实验和凝胶过滤进一步获得了支持谷胱甘肽还原酶共价修饰的证据。提出了失活的动力学方案，并结合目前关于亲和试剂使谷胱甘肽还原酶失活的概念，讨论了体外数据与先前体内研究的相关性。
