Wang Junqing, Ren Xudong, Wang Ruiming, Su Jing, Wang Feng
Faculty of Light Industry, Province Key Laboratory of Microbial Engineering, Qilu University of Technology , Jinan 250353, P.R. China.
State Key Laboratory of Microbial Technology, School of Life Sciences, Shandong University , Jinan, Shandong 250100, P.R. China.
J Agric Food Chem. 2017 Sep 6;65(35):7726-7735. doi: 10.1021/acs.jafc.7b02732. Epub 2017 Aug 23.
Trehalose has important applications in the food industry and pharmaceutical manufacturing. The thermostable enzyme trehalose synthase from Thermobaculum terrenum (TtTS) catalyzes the reversible interconversion of maltose and trehalose. Here, we investigated the structural characteristics of TtTS in complex with the inhibitor TriS. TtTS exhibits the typical three domain glycoside hydrolase family 13 structure. The catalytic cleft consists of Asp202-Glu244-Asp310 and various conserved substrate-binding residues. However, among trehalose synthases, TtTS demonstrates obvious thermal stability. TtTS has more polar (charged) amino acids distributed on its protein structure surface and more aromatic amino acids buried within than other mesophilic trehalose synthases. Furthermore, TtTS structural analysis revealed four potential metal ion-binding sites rather than the two in a homologous structure. These factors may render TtTS relatively more thermostable among mesophilic trehalose synthases. The detailed thermophilic enzyme structure provided herein may provide guidance for further protein engineering in the design of stabilized enzymes.
海藻糖在食品工业和制药生产中具有重要应用。来自陆地嗜热芽孢杆菌（TtTS）的热稳定酶海藻糖合酶催化麦芽糖和海藻糖的可逆相互转化。在此，我们研究了TtTS与抑制剂TriS复合物的结构特征。TtTS呈现出典型的糖苷水解酶家族13的三结构域结构。催化裂隙由Asp202 - Glu244 - Asp310以及各种保守的底物结合残基组成。然而，在海藻糖合酶中，TtTS表现出明显的热稳定性。与其他嗜温性海藻糖合酶相比，TtTS在其蛋白质结构表面分布有更多的极性（带电荷）氨基酸，并且埋藏在内部的芳香族氨基酸更多。此外，TtTS的结构分析揭示了四个潜在的金属离子结合位点，而不是同源结构中的两个。这些因素可能使TtTS在嗜温性海藻糖合酶中相对更具热稳定性。本文提供的详细嗜热酶结构可能为稳定化酶设计中的进一步蛋白质工程提供指导。
