A Proton Wire and Water Channel Revealed in the Crystal Structure of Isatin Hydrolase
A Proton Wire and Water Channel Revealed in the Crystal Structure of Isatin Hydrolase
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DOI：
10.1074/jbc.m114.568824
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发表时间：
2014-08-01
影响因子：
4.8
通讯作者：
Morth, J. Preben
中科院分区：
文献类型：
--
作者：
Bjerregaard-Andersen, Kaare;Sommer, Theis;Morth, J. Preben
本文报道了聚合拉布仑藻靛红水解酶的高分辨晶体结构和产物状态。这些是该折叠的功能特征的金属依赖性水解酶的第一结构。靛红水解酶将靛红转化为靛红酸，并且属于包括细菌犬尿氨酸甲酰胺酶的新型金属酶家族。由结合的硫代靛红模仿的产物状态揭示了将硫代靛红桥接到相邻水通道中的质子线的水分子，从而仅当产物形成时才允许由反应释放的质子逃逸。靛红水解酶亚型B中存在的功能性质子线代表了所有水解酶共有的独特催化特征，在此首次被捕获并可视化。协调硫代靛红所需的局部分子环境允许在原核生物界中更强和更有信心地鉴定编码靛红水解酶的正向同源基因。在人类肠道细菌中发现的靛红水解酶直向同源物提出了关于吲哚-3-乙酸降解途径是否存在于人类肠道植物群中的问题。
The high resolution crystal structures of isatin hydrolase from Labrenzia aggregata in the apo and the product state are described. These are the first structures of a functionally characterized metal-dependent hydrolase of this fold. Isatin hydrolase converts isatin to isatinate and belongs to a novel family of metalloenzymes that include the bacterial kynurenine formamidase. The product state, mimicked by bound thioisatinate, reveals a water molecule that bridges the thioisatinate to a proton wire in an adjacent water channel and thus allows the proton released by the reaction to escape only when the product is formed. The functional proton wire present in isatin hydrolase isoform b represents a unique catalytic feature common to all hydrolases is here trapped and visualized for the first time. The local molecular environment required to coordinate thioisatinate allows stronger and more confident identification of orthologous genes encoding isatin hydrolases within the prokaryotic kingdom. The isatin hydrolase orthologues found in human gut bacteria raise the question as to whether the indole-3-acetic acid degradation pathway is present in human gut flora.