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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Structural characterization of tartrate dehydrogenase: a versatile enzyme catalyzing multiple reactions.
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Structural characterization of tartrate dehydrogenase: a versatile enzyme catalyzing multiple reactions.

机译：酒石酸的结构特征脱氢酶:一个多才多艺的酶催化多重反应。

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摘要

The first structure of an NAD-dependent tartrate dehydrogenase (TDH) has been solved to 2 A resolution by single anomalous diffraction (SAD) phasing as a complex with the intermediate analog oxalate, Mg(2+) and NADH. This TDH structure from Pseudomonas putida has a similar overall fold and domain organization to other structurally characterized members of the hydroxy-acid dehydrogenase family. However, there are considerable differences between TDH and these functionally related enzymes in the regions connecting the core secondary structure and in the relative positioning of important loops and helices. The active site in these complexes is highly ordered, allowing the identification of the substrate-binding and cofactor-binding groups and the ligands to the metal ions. Residues from the adjacent subunit are involved in both the substrate and divalent metal ion binding sites, establishing a dimer as the functional unit and providing structural support for an alternating-site reaction mechanism. The divalent metal ion plays a prominent role in substrate binding and orientation, together with several active-site arginines. Functional groups from both subunits form the cofactor-binding site and the ammonium ion aids in the orientation of the nicotinamide ring of the cofactor. A lysyl amino group (Lys192) is the base responsible for the water-mediated proton abstraction from the C2 hydroxyl group of the substrate that begins the catalytic reaction, followed by hydride transfer to NAD. A tyrosyl hydroxyl group (Tyr141) functions as a general acid to protonate the enolate intermediate. Each substrate undergoes the initial hydride transfer, but differences in substrate orientation are proposed to account for the different reactions catalyzed by TDH.
机译：第一个结构NAD-dependent酒石酸脱氢酶2 (TDH)已经解决了决议由单一反常衍射(SAD)逐步与中间一个复杂的模拟草酸、镁(2 +)和NADH。假单胞菌putida也有类似的整体折域组织结构具有羟基的成员脱氢酶家族。TDH这些相当大的差异功能相关的酶的地区连接二级结构和核心循环和相对定位的重要螺旋线。高度有序,使识别的substrate-binding和cofactor-binding组金属离子和配体。邻亚基参与了衬底和二价金属离子结合位点,建立一个功能单元和二聚体为一个提供结构支撑alternating-site反应机制。金属离子在衬底中起着重要的作用绑定和取向,几个在一起活性部位精氨酸。两个亚基形成cofactor-binding网站铵离子艾滋病的取向烟酰胺环的代数余子式。集团(Lys192)基地负责从C2 water-mediated质子抽象羟基的衬底的开始催化反应,其次是氢化物转移河畔。一般酸使质子化的功能烯醇化物中间体。最初的氢化物转移,但差异衬底取向提出了占由TDH不同的催化反应。

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