Glutathione Transferase Classes Alpha, Pi, and Mu: GSH Activation Mechanism
Glutathione Transferase Classes Alpha, Pi, and Mu: GSH Activation Mechanism
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DOI：
10.1021/jp1053875
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发表时间：
2010-10-14
影响因子：
3.3
通讯作者：
Ramos, Maria Joao
中科院分区：
文献类型：
--
作者：
Dourado, Daniel F. A. R.;Fernandes, Pedro Alexandrino;Ramos, Maria Joao
自20世纪60年代初以来，谷胱甘肽转移酶（GST）已被描述为解毒酶。事实上，GST是参与亲电性异生物质/内源性化合物代谢的最重要的酶。这些酶能够催化谷胱甘肽（GSH）硫硫醇盐与各种亲电子底物的亲核加成，形成毒性较小且可溶性更高的化合物。胞质类α、pi和mu是研究最广泛的GST。然而，许多催化事件仍然知之甚少。在目前的工作中，我们已经诉诸密度泛函理论（DFT）和潜在的平均力（PM F）的计算，以确定GSH激活机制的GsTP 1-I和GSTMI-1同工酶。对于GSTPI-1酶，我们已经证明，一个水分子，在GSH的初始构象重排后，可以帮助GSH半胱氨酸巯基（GSH-SH）和GSH谷氨酸α羧酸（GSH-COO-）基团之间的质子转移。与质子转移有关的能垒为11.36 kcal·mol（-1）。GSTMI-1酶显示出与先前同工酶完全不同的行为。在这种情况下，位于GSH-SH和His 107的N原子之间的两个水分子，像桥一样工作，能够促进这两个活性基团之间的质子转移，能量势垒为7.98 kcal。mol（-1）。我们的结果与所有的酶动力学和诱变实验研究相一致。
Since the early 1960s, glutathione transferases (GSTs) have been described as detoxification enzymes. In fact, GSTs are the most important enzymes involved in the metabolism of electrophilic xenobiotic/endobiotic compounds. These enzymes are able to catalyze the nucleophilic addition of glutathione (GSH) sulfur thiolate to a wide range of electrophilic substrates, building up a less toxic and more soluble compound. Cytosolic classes alpha, pi, and mu are the most extensively studied GSTs. However, many of the catalytic events are still poorly understood. In the present work, we have resorted to density functional theory (DFT) and to potential of mean force (PM F) calculations to determine the GSH activation mechanism of GsTP1-I and GSTMI-1 isoenzymes. For the GSTPI-1 enzyme, we have demonstrated that a water molecule, after an initial conformational rearrangement of GSH, can assist a proton transfer between the GSH cysteine thiol (GSH-SH) and the GSH glutamate alpha carboxylate (GSH-COO-) groups. The energy barrier associated with the proton transfer is 11.36 kcal.mol(-1). The GSTMI-1 enzyme shows a completely different behavior from the previous isoenzyme. In this case, two water molecules, positioned between the GSH-SH and the N atom of His 107, working like a bridge, are able to promote the proton transfer between these two active groups with an energy barrier of 7.98 kcal. mol(-1). All our results are consistent with all the enzymes kinetics and mutagenesis experimental studies.