Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia.
PLoS One. 2013 Apr 9;8(4):e60324. doi: 10.1371/journal.pone.0060324. Print 2013.
Glutathione transferases (GSTs) are dimeric enzymes containing one active-site per monomer. The omega-class GSTs (hGSTO1-1 and hGSTO2-2 in humans) are homodimeric and carry out a range of reactions including the glutathione-dependant reduction of a range of compounds and the reduction of S-(phenacyl)glutathiones to acetophenones. Both types of reaction result in the formation of a mixed-disulfide of the enzyme with glutathione through the catalytic cysteine (C32). Recycling of the enzyme utilizes a second glutathione molecule and results in oxidized glutathione (GSSG) release. The crystal structure of an active-site mutant (C32A) of the hGSTO1-1 isozyme in complex with GSSG provides a snapshot of the enzyme in the process of regeneration. GSSG occupies both the G (GSH-binding) and H (hydrophobic-binding) sites and causes re-arrangement of some H-site residues. In the same structure we demonstrate the existence of a novel "ligandin" binding site deep within in the dimer interface of this enzyme, containing S-(4-nitrophenacyl)glutathione, an isozyme-specific substrate for hGSTO1-1. The ligandin site, conserved in Omega class GSTs from a range of species, is hydrophobic in nature and may represent the binding location for tocopherol esters that are uncompetitive hGSTO1-1 inhibitors.
谷胱甘肽转移酶（GSTs）是二聚体酶，每个单体含有一个活性位点。ω 类 GSTs（人类中的 hGSTO1-1 和 hGSTO2-2）是同源二聚体，可进行多种反应，包括依赖谷胱甘肽的一系列化合物还原以及 S-（苯乙酰基）谷胱甘肽还原为苯乙酮。这两种类型的反应都会导致酶与谷胱甘肽通过催化半胱氨酸（C32）形成混合二硫键。酶的回收利用第二个谷胱甘肽分子，并导致氧化型谷胱甘肽（GSSG）的释放。与 GSSG 结合的 hGSTO1-1 同工酶活性位点突变体（C32A）的晶体结构提供了酶在再生过程中的快照。GSSG 占据 G（谷胱甘肽结合）和 H（疏水性结合）两个位点，并导致一些 H 位残基的重排。在同一结构中，我们证明了在该酶的二聚体界面深处存在一个新的“配体结合”位点，其中含有 S-（4-硝基苯乙酰基）谷胱甘肽，这是 hGSTO1-1 的同工酶特异性底物。配体结合位点在来自多种物种的ω 类 GSTs 中保守，本质上是疏水性的，可能代表了生育酚酯的结合位置，生育酚酯是竞争性 hGSTO1-1 抑制剂。
