Properties and structures of β-glucuronidases with different transformation types of glycyrrhizin
Properties and structures of β-glucuronidases with different transformation types of glycyrrhizin
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DOI：
10.1039/c5ra11484e
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发表时间：
2015-08
期刊：
影响因子：
3.9
通讯作者：
Xiaoyang Wang;Yanli Liu;Chao Wang;Xudong Feng;Chun Li
中科院分区：
文献类型：
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作者：
Xiaoyang Wang;Yanli Liu;Chao Wang;Xudong Feng;Chun Li
葡萄糖醛酸苷酶(β-GLucuronidase，GUS)被广泛用于β连接的葡萄糖醛酸苷的水解酶，以生成各种有价值的衍生物。本研究比较了三种不同类型甘草酸(GL)水解物的GUS，分别是来自紫云英菌株Li-3的PGUS、来自A.terreus Li-20的AtGUS和来自A.Ustus Li-62的Augus。PGUS、ATGUS和AUGUS的Km值分别为0.328、3.61和0.429 mm。这些结果表明，在三种GUS中，AtGUS对GL的亲和力最低，而PGUS和Augus对GL的亲和力相似。然而，Vmax/Km值表明，Augus对GL的催化效率最高，因此它是一种有效的GL生物转化的生物催化剂。序列性质分析表明，三个GU具有一些特殊的不同序列特征，但这并不是导致催化类型差异的主要原因。同源模型分析表明，PGUS、AtGUS和AUGUS的不同GL转化类型可能是由于其苷元结合口袋周围的细菌环位置不同所致。这些结果不仅可以帮助我们更好地了解GUS的催化多样性，而且对我们重新设计GUS的催化多样性也有重要的指导意义。
β-Glucuronidase (GUS) has been widely used to hydrolyze β-linked glucuronides to generate various valuable derivatives. In this study, the GUS from three fungi (PGUS from P. purpurogenum Li-3, AtGUS from A. terreus Li-20 and AuGUS from A. ustus Li-62) with significantly different types of glycyrrhizin (GL) hydrolysis were comparatively investigated. The Km values of PGUS, AtGUS and AuGUS were 0.328, 3.61 and 0.429 mM respectively. These results indicated that AtGUS showed the lowest affinity for GL among the three kinds of GUS, while PGUS and AuGUS had a similar affinity for GL. Nevertheless, the Vmax/Km values showed that AuGUS had the highest catalytic efficiency for GL hydrolysis, so it was supposed to be an efficient biocatalysis for GL biotransformation. The sequence properties analysis demonstrated that the three GUS had some special different sequence characteristics, but that is not the key reason for the discrepancy in catalytic type. The homologous modeling analysis indicated that various GL transformation types of PGUS, AtGUS and AuGUS were likely caused by the different positions of bacterial loops surrounding their aglycone binding pocket. These results can not only help us to better understand the catalytic diversity of GUS, but also give us an important guide to redesign the catalytic diversity of GUS.