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首页> 外文期刊>Acta crystallographica, Section D. Biological crystallography >Enantioselective oxidation of galactitol 1-phosphate by galactitol-1-phosphate 5-dehydrogenase from Escherichia coli
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Enantioselective oxidation of galactitol 1-phosphate by galactitol-1-phosphate 5-dehydrogenase from Escherichia coli

机译：大肠杆菌中的半乳糖醇-1-磷酸酯5-脱氢酶对半乳糖醇1-磷酸酯的对映选择性氧化

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摘要

Galactitol-1-phosphate 5-dehydrogenase (GPDH) is a polyol dehydrogenase that belongs to the medium-chain dehydrogenase/reductase (MDR) superfamily. It catalyses the Zn2+- and NAD(+)-dependent stereoselective dehydrogenation of l-galactitol 1-phosphate to D-tagatose 6-phosphate. Here, three crystal structures of GPDH from Escherichia coli are reported: that of the open state of GPDH with Zn2+ in the catalytic site and those of the closed state in complex with the polyols Tris and glycerol, respectively. The closed state of GPDH reveals no bound cofactor, which is at variance with the conformational transition of the prototypical mammalian liver alcohol dehydrogenase. The main intersubunit-contacting interface within the GPDH homodimer presents a large internal cavity that probably facilitates the relative movement between the subunits. The substrate analogue glycerol bound within the active site partially mimics the catalytically relevant backbone of galactitol 1-phosphate. The glycerol binding mode reveals, for the first time in the polyol dehydrogenases, a pentacoordinated zinc ion in complex with a polyol and also a strong hydrogen bond between the primary hydroxyl group and the conserved Glu144, an interaction originally proposed more than thirty years ago that supports a catalytic role for this acidic residue.
机译：半乳糖-1-磷酸5-脱氢酶（GPDH）是一种多元醇脱氢酶，属于中链脱氢酶/还原酶（MDR）超家族。它催化1-半乳糖醇1-磷酸锌的Zn2 +-和NAD（+）-依赖性立体选择性脱氢为6-磷酸D-塔格糖。在此，报道了来自大肠杆菌的GPDH的三个晶体结构：在催化位点具有Zn 2+的GPDH的开放状态和与多元醇Tris和甘油复合的闭合状态的晶体结构。 GPDH的封闭状态显示没有结合的辅因子，这与典型的哺乳动物肝脏酒精脱氢酶的构象转变不同。 GPDH同型二聚体中主要的亚基间接触界面呈现出较大的内部空腔，这可能会促进亚基之间的相对运动。结合在活性位点上的底物类似物甘油部分模拟了半乳糖醇1-磷酸的催化相关主链。甘油的结合模式首次揭示了在多元醇脱氢酶中与多元醇复合的五配位锌离子以及伯羟基与保守Glu144之间的强氢键，这种相互作用最初是在三十多年前提出的，支持该酸性残基的催化作用。

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