New insight into the catalytic properties of bile salt hydrolase
New insight into the catalytic properties of bile salt hydrolase
复制标题
对胆汁盐水解酶催化特性的新见解
DOI：
10.1016/j.molcatb.2013.06.010
复制
发表时间：
2013-12-01
影响因子：
--
通讯作者：
Chen, Jian
中科院分区：
文献类型：
--
作者：
Bi, Jie;Fang, Fang;Chen, Jian
胆盐水解酶（BSH）是一种解结合胆汁的酶，在降低血液胆固醇水平中起着重要作用。来自不同来源的BSH酶在特性、底物偏好和比催化活性方面不同。本研究从唾液乳杆菌中异源表达并纯化了两种BSH酶（BSH 1和BSH 2）。通过分子排阻色谱测定了它们的相对分子质量，确定它们均为同源四聚体。BSH 1在5.5 ~ 7.0范围内表现出较宽的最适pH值，而BSH 2在5.5 ~ 6.0范围内表现出较窄的最适pH值。对纯化的BSH 1和BSH 2的动力学研究表明，细菌BSH酶是一种变构酶，并首次揭示了它们在正协同性、催化效率和底物选择性方面的显著差异。与BSH在无二硫苏糖醇存在下的酶促反应相反，BSH 1和BSH 2的动力学曲线类似于二硫苏糖醇存在下的Michaelis-Menten动力学的双曲线形式。(C)2013年爱思唯尔RV。All rights reserved.
Bile salt hydrolase (BSH), the enzyme deconjugating bile potentially plays an important role in reduction of blood cholesterol level. BSH enzymes from various sources differ in characteristics, substrates preference and specific catalytic activity. In this study, two BSH enzymes (BSH1 and BSH2) from Lactobacillus salivarius were heterologously expressed and purified. Both of them were characterized as homotetramer according to their molecular weight from size exclusion chromatograph. BSH1 showed a broad pH optimum over the range from 5.5 to 7.0, while a narrower range of pH optimum from 5.5 to 6.0 for BSH2 was detected. The enzymatic kinetics of the purified BSH1 and BSH2 have demonstrated BSH enzymes from bacteria were allosteric enzymes, and have also revealed their striking differences in positive cooperativity, catalytic efficiency and substrate preference for the first time. In contrast to the enzymatic reactions of BSH in the absence of dithiothreitol, the kinetics curves of BSH1 and BSH2 were similar to hyperbolic forms of Michaelis-Menten kinetics in the presence of dithiothreitol. (C) 2013 Elsevier RV. All rights reserved.