Yuan Shuai, Liu Ming, Yang Yan, He Jiu-Ming, Wang Ya-Nan, Kong Jian-Qiang
Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College (State Key Laboratory of Bioactive Substance and Function of Natural Medicines & Ministry of Health Key Laboratory of Biosynthesis of Natural Products), Beijing 100050, China.
Genes (Basel). 2018 Jun 28;9(7):327. doi: 10.3390/genes9070327.
Aurone glycosides display a variety of biological activities. However, reports about glycosyltransferases (GTs) responsible for aurones glycosylation are limited. Here, the transcriptome-wide discovery and identification of an aurone glycosyltransferase with glycosidase activity is reported. Specifically, a complementary DNA (cDNA), designated as OsUGT1, was isolated from the plant based on transcriptome mining. Conserved domain (CD)-search speculated OsUGT1 as a flavonoid GT. Phylogenetically, OsUGT1 is clustered as the same phylogenetic group with a putative 5,6-dihydroxyindoline-2-carboxylic acid (-DOPA) 5--glucosyltransferase, suggesting OsUGT1 may be an aurone glycosyltransferase. The purified OsUGT1 was therefore used as a biocatalyst to incubate with the representative aurone sulfuretin. In vitro enzymatic analyses showed that OsUGT1 was able to catalyze sulfuretin to form corresponding monoglycosides, suggesting OsUGT1 was indeed an aurone glycosyltransferase. OsUGT1 was observed to be a flavonoid GT, specific for flavonoid substrates. Moreover, OsUGT1 was demonstrated to display transglucosylation activity, transferring glucosyl group to sulfuretin via -Nitrophenyl-β-d-glucopyranoside (NP-β-Glc)-dependent fashion. In addition, OsUGT1-catalyzed hydrolysis was observed. This multifunctionality of OcUGT1 will broaden the application of OcUGT1 in glycosylation of aurones and other flavonoids.
橙酮糖苷具有多种生物活性。然而，关于负责橙酮糖基化的糖基转移酶（GTs）的报道有限。在此，报告了对具有糖苷酶活性的橙酮糖基转移酶进行全转录组范围的发现和鉴定。具体而言，基于转录组挖掘从植物中分离出一个名为OsUGT1的互补DNA（cDNA）。保守结构域（CD）搜索推测OsUGT1为类黄酮GT。在系统发育上，OsUGT1与一种假定的5,6 - 二羟基吲哚 - 2 - 羧酸（-DOPA）5 - -葡糖基转移酶聚集在同一系统发育组中，表明OsUGT1可能是一种橙酮糖基转移酶。因此，纯化的OsUGT1被用作生物催化剂与代表性橙酮硫磺菊素一起孵育。体外酶分析表明，OsUGT1能够催化硫磺菊素形成相应的单糖苷，表明OsUGT1确实是一种橙酮糖基转移酶。观察到OsUGT1是一种类黄酮GT，对类黄酮底物具有特异性。此外，OsUGT1被证明具有转糖基化活性，通过 - 硝基苯基 - β - D - 吡喃葡萄糖苷（NP - β - Glc）依赖性方式将葡萄糖基转移到硫磺菊素上。此外，还观察到OsUGT1催化的水解作用。OsUGT1的这种多功能性将拓宽OsUGT1在橙酮和其他类黄酮糖基化中的应用。
