Norwegian Center for Molecular Medicine, Nordic EMBL Partnership University of Oslo, Gaustadalléen 21, 0349, Oslo, Norway.
Department of Chemistry, University of Oslo, Sem Sælands vei 26, 0371, Oslo, Norway.
Sci Rep. 2018 Aug 30;8(1):13104. doi: 10.1038/s41598-018-31259-y.
The catalytic mechanism of the cyclic amidohydrolase isatin hydrolase depends on a catalytically active manganese in the substrate-binding pocket. The Mn ion is bound by a motif also present in other metal dependent hydrolases like the bacterial kynurenine formamidase. The crystal structures of the isatin hydrolases from Labrenzia aggregata and Ralstonia solanacearum combined with activity assays allow for the identification of key determinants specific for the reaction mechanism. Active site residues central to the hydrolytic mechanism include a novel catalytic triad Asp-His-His supported by structural comparison and hybrid quantum mechanics/classical mechanics simulations. A hydrolytic mechanism for a Mn dependent amidohydrolases that disfavour Zn as the primary catalytically active site metal proposed here is supported by these likely cases of convergent evolution. The work illustrates a fundamental difference in the substrate-binding mode between Mn dependent isatin hydrolase like enzymes in comparison with the vast number of Zn dependent enzymes.
色胺酮水解酶的催化机制依赖于底物结合口袋中具有催化活性的锰。Mn 离子由一个基序结合，该基序也存在于其他依赖金属的水解酶中，如细菌色氨酸-formamidase。来自聚球藻和茄属雷尔氏菌的色胺酮水解酶的晶体结构与活性测定相结合，可鉴定出特定于反应机制的关键决定因素。对水解机制至关重要的活性位点残基包括一个新颖的催化三联体 Asp-His-His，这一结构是通过结构比较和混合量子力学/经典力学模拟得到的。这里提出的 Mn 依赖性酰胺水解酶的水解机制不赞成 Zn 作为主要的催化活性位点金属，这一机制得到了这些趋同进化的可能案例的支持。这项工作说明了 Mn 依赖性色胺酮水解酶样酶与大量 Zn 依赖性酶之间在底物结合模式上的根本区别。
