Expanded investigations of the aglycon promiscuity and catalysis characteristic of flavonol 3-O-rhamnosyltransferase AtUGT78D1 from Arabidopsis thaliana
Expanded investigations of the aglycon promiscuity and catalysis characteristic of flavonol 3-O-rhamnosyltransferase AtUGT78D1 from Arabidopsis thaliana
复制标题
拟南芥黄酮醇 3-O-鼠李糖基转移酶 AtUGT78D1 的苷元混杂性和催化特性的扩展研究
DOI：
10.1039/c6ra16251g
复制
发表时间：
2016-01-01
期刊：
影响因子：
3.9
通讯作者：
Tu, Pengfei
中科院分区：
文献类型：
--
作者：
Mo, Ting;Liu, Xiao;Tu, Pengfei
鼠李糖甙通常具有比其苷元更好的生物利用度和改善的溶解度，并且是生物活性天然产物的主要来源。然而，鼠李糖苷的生物合成受到商业上昂贵的UDP-鼠李糖（UDP-Rha）供体和缺乏通用的鼠李糖基转移酶的阻碍。本研究以UDP-葡萄糖（UDP-Glc）为底物，通过两步酶促反应构建了一个高效的UDP-Rha生产系统。使用获得的UDP-Rha/UDP-Glc的广泛的体外酶促测定和制备反应突出了所报道的鼠李糖基转移酶AtUGT 78 D1的稳健的糖基化混杂性。基于HPLC-UV和HR-MS分析，属于7种结构类型的30种测试的芳香族化合物，包括黄酮类化合物、黄酮苷类化合物、苯乙基色酮、二苯甲酮、香豆素、木脂素和蒽醌，被AtUGT 78 D1接受以进行相应的鼠李糖基化和/或葡萄糖基化，在不同位置具有一个或多个糖基取代。进一步的制备反应扩展了AtUGT 78 D1的催化特性，因为它可以催化黄酮醇3-OH位的鼠李糖基化，黄酮黄芩素7-OH位的葡萄糖基化，以及多种类型的芳香族化合物的多羟基取代。有趣的是，观察到AtUGT 78 D1独特的可逆催化活性，并且其已有效地用于所需鼠李糖苷的一锅法鼠李糖基化。AtUGT 78 D1对多种“类药物”支架的酶促鼠李糖基化反应以及植物鼠李糖基转移酶对“一锅法”鼠李糖基化反应的双向催化作用未见报道，表明AtUGT 78 D1有望成为化学-酶促合成多种生物活性鼠李糖基化衍生物的通用有效工具。
Rhamnosides usually possess better bioavailabilities and improved solubilities compared with their aglycons and are a major source of bioactive natural products. However, biosynthesis of rhamnosides is hindered by the commercially expensive UDP-rhamnose (UDP-Rha) donor and a lack of universal rhamnosyltransferases. In the present study, an efficient UDP-Rha production system via a two-step enzymatic reactions using UDP-glucose (UDP-Glc) as a substrate was constructed. Extensive in vitro enzymatic assays and preparative reactions using the obtained UDP-Rha/UDP-Glc highlighted the robust glycosylation promiscuity of the reported rhamnosyltransferase AtUGT78D1. Based on HPLC-UV and HR-MS analyses, 30 of the tested aromatic compounds belonging to 7 structural types, including flavonoids, flavonoid glycosides, phenylethyl chromones, benzophenones, coumarins, lignanoids, and anthraquinones, were accepted by AtUGT78D1 to conduct the corresponding rhamnosylation and/or glucosylation with one or more glycosyl substitutions at different positions. Further preparative reactions expanded the catalytic characteristic of AtUGT78D1 since it can catalyse the rhamnosylation at the 3-OH position of the flavonols, glucosylation at the 7-OH position of the flavone baicalein, and multiple hydroxyl substitutions for diverse types of aromatics. Interestingly, a unique reversible catalysis activity of AtUGT78D1 was observed, and it has been effectively used in one-pot rhamnosylation of the desired rhamnoside. The enzymatic rhamnosylations of diverse “drug-like” scaffolds as well as bidirectional catalysis for one-pot rhamnosylations by plant rhamnosyltransferase were rarely reported before, which indicated that AtUGT78D1 was expected to be a universal and effective tool for chemo-enzymatic synthesis of diverse bioactive rhamnosylated derivatives for drug discovery.