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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Near-atomic resolution structures of urate oxidase complexed with its substrate and analogues: the protonation state of the ligand.
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Near-atomic resolution structures of urate oxidase complexed with its substrate and analogues: the protonation state of the ligand.

机译：Near-atomic决议尿酸氧化酶的结构包裹着它的底物类似物:质子化作用的配体。

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摘要

Urate oxidase (uricase; EC 1.7.3.3; UOX) from Aspergillus flavus catalyzes the oxidation of uric acid in the presence of molecular oxygen to 5-hydroxyisourate in the degradation cascade of purines; intriguingly, catalysis proceeds using neither a metal ion (Fe, Cu etc.) nor a redox cofactor. UOX is a tetrameric enzyme with four active sites located at the interface of two subunits; its structure was refined at atomic resolution (1 A) using new crystal data in the presence of xanthine and at near-atomic resolution (1.3-1.7 A) in complexes with the natural substrate (urate) and two inhibitors: 8-nitroxanthine and 8-thiouric acid. Three new features of the structural and mechanistic behaviour of the enzyme were addressed. Firstly, the high resolution of the UOX-xanthine structure allowed the solution of an old structural problem at a contact zone within the tetramer; secondly, the protonation state of the substrate was determined from both a halochromic inhibitor complex (UOX-8-nitroxanthine) and from the H-atom distribution in the active site, using the structures of the UOX-xanthine and the UOX-uric acid complexes; and thirdly, it was possible to extend the general base system, characterized by the conserved catalytic triad Thr-Lys-His, to a large water network that is able to buffer and shuttle protons back and forth between the substrate and the peroxo hole along the reaction pathway.
机译：尿酸盐氧化酶(尿酸酶;黄曲霉催化的氧化尿酸在分子氧的存在5-hydroxyisourate退化的级联嘌呤;既没有金属离子(铁、铜等)也不是氧化还原代数余子式。活动地点位于界面的两个子单元;决议(1)使用新的水晶中的数据黄嘌呤和near-atomic分辨率(1.3 - -1.7)的复合物天然底物(尿酸盐)和两种抑制剂:8-nitroxanthine 8-thiouric酸。的结构和机械特性行为的酶被解决。的高分辨率UOX-xanthine结构允许一个古老的结构性问题的解决方案在接触区域内四聚物;质子化作用的底物决定从halochromic抑制剂从氢原子,复杂(UOX-8-nitroxanthine)和分布在活动网站,使用UOX-xanthine和UOX-uric结构酸复合物;扩展的一般基本系统的特征守恒的催化三Thr-Lys-His,大型网络能够缓冲和水航天飞机质子之间来回反应底物和peroxo洞途径。

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