Bacterial exopolymer Levan (β-(2,6) polyfructan) synthesized by levansucrase has attracted interest for various applications due to its low intrinsic viscosity compared with other polysaccharides. We report a novel levansucrase (Lsc) isolated from Sphingobium chunbukense DJ77 and verify its biochemical characteristics by comparative analysis of molecular docking analysis (MOE) and catalytic residue analysis. The complete sequence of the Lsc encoding gene (lsc) was cloned under the direction of the T7 promoter and purified in an Escherichia coli BL21 (DE3) protein expression system. The enzyme activity analysis and ligand docking MOE study of S. chungbukense DJ77 Lsc revealed that Arg 77, Ser112, Arg 195, Asp196, Glu257, and Gln275 were involved in the sucrose binding and splitting as well as transfructosylation activity. A catalytic comparison of Lsc of S. chungbukense DJ77 with the results of site-directed mutational analysis indicated that Gln275 may coordinate a favorable substrate binding environment, offering broad pH resistance in the range of 5–10. The results suggest that the recombinant E. coli carrying S. chungbukense DJ77 Lsc might produce levan under the regular growth conditions with less need for pH manipulation.

中文翻译：

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从分子对接分析和果聚糖蔗糖酶的生化评估Sphingobium chungbukense DJ77

由左旋蔗糖酶合成的细菌外聚合物左旋（Lev（β-（2,6）聚果聚糖）由于与其他多糖相比具有较低的固有粘度而引起了广泛的兴趣。我们报告了一种新型的从蔗糖单胞菌DJ77分离出的甘蔗糖酶（Lsc），并通过分子对接分析（MOE）和催化残留分析的比较分析验证了其生化特性。Lsc编码基因（lsc）的完整序列在T7启动子的指导下克隆，并在大肠杆菌BL21（DE3）蛋白表达系统中纯化。中华绒螯蟹的酶活性分析和配体对接MOE研究DJ77 Lsc揭示了Arg 77，Ser112，Arg 195，Asp196，Glu257和Gln275参与了蔗糖的结合和分裂以及果糖基化活性。的LSC的催化比较S. chungbukense DJ77用定点突变分析的结果表明，Gln275可以协调有利的底物结合的环境中，在5-10的范围内提供宽的pH电阻。结果表明，重组大肠杆菌携带S. chungbukense DJ77 LSC可能会产生的常规生长条件下果聚糖与用于pH操纵不太需要。