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首页> 外文期刊>Journal of Molecular Biology >The crystal structure of enamidase: a bifunctional enzyme of the nicotinate catabolism.
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The crystal structure of enamidase: a bifunctional enzyme of the nicotinate catabolism.

机译：烯酰胺酶的晶体结构：烟酸酯分解代谢的双功能酶。

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摘要

The hydrolysis of 1,4,5,6-tetrahydro-6-oxonicotinate to 2-formylglutarate is a central step in the catabolism of nicotinate in several Clostridia and Proteobacteria. This reaction is catalyzed by the novel enzyme enamidase, a new member of the amidohydrolase superfamily as indicated by its unique reaction, sequence relationship, and the stoichiometric binding of iron and zinc. A hallmark of enamidase is its capability to catalyze a two-step reaction: the initial decyclization of 1,4,5,6-tetrahydro-6-oxonicotinate leading to 2-(enamine)glutarate followed by an additional hydrolysis step yielding (S)-2-formylglutarate. Here, we present the crystal structure of enamidase from Eubacterium barkeri at 1.9 A resolution, providing a structural basis for catalysis and suggesting a mechanism for its exceptional activity and enantioselectivity. The enzyme forms a 222-symmetric tetramer built up by a dimer of dimers. Each enamidase monomer consists of a composite beta-sandwich domain and an (alpha/beta)(8)-TIM-barrel domain harboring the active site. With its catalytic binuclear metal center comprising both zinc and iron ions, enamidase represents a special case of subtype II amidohydrolases.
机译：1,4,5,6-四氢-6-氧代烟酸酯的水解为戊二酸2-甲酰基酯是数个梭菌和变形杆菌中烟酸酯分解代谢的重要步骤。该反应由新型酶烯酰胺酶催化，该酶是酰胺水解酶超家族的新成员，如其独特的反应，序列关系以及铁和锌的化学计量结合所表明的那样。烯酰胺酶的标志是其催化两步反应的能力：1,4,5,6-四氢-6-氧代烟酸酯的初始脱环反应生成戊二酸2-（烯胺），然后进行额外的水解步骤，得到（S） -2-甲酰基戊二酸酯。在这里，我们以1.9 A的分辨率呈现来自巴氏杆菌（Eubacterium barkeri）的烯胺酶的晶体结构，为催化提供了结构基础，并提出了其卓越活性和对映选择性的机制。该酶形成由二聚体的二聚体建立的222-对称的四聚体。每个烯酰胺酶单体均由复合β-三明治结构域和一个带有活性位点的（α/β）（8）-TIM-桶结构域组成。烯酰胺酶的催化双核金属中心包含锌和铁离子，是II型酰胺水解酶的特例。

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