Ji Xiaoyu, Lin Shumin, Chen Yuanyuan, Liu Jiawei, Yun Xiaoyun, Wang Tiancheng, Qin Jialiang, Luo Chaoquan, Wang Kui, Zhao Zhongxiang, Zhan Ruoting, Xu Hui
Research Center of Chinese Herbal Resource Science and Engineering, Guangzhou University of Chinese Medicine, Guangzhou, China.
Key Laboratory of Chinese Medicinal Resource from Lingnan (Guangzhou University of Chinese Medicine), Ministry of Education, Guangzhou, China.
Front Plant Sci. 2020 May 20;11:612. doi: 10.3389/fpls.2020.00612. eCollection 2020.
is a medicinal plant that is used extensively in southern China. The plant contains ursane-type triterpenoids and triterpenoid saponins which are known to be responsible for its pharmacological activities. Previously, a transcriptomic analysis of was carried out and the gene 1, which is important in the formation of the core structure α-amyrin, was identified. However, the genes related to the subsequent derivatization of the core structures of the triterpenoid remain largely unknown. Herein, we describe the cloning and functional characterization of an amyrin 28-carboxylase IaAO1 (designated as IaCYP716A210) and a glycosyltransferase IaAU1 (designated as UGT74AG5), based on transcriptomic data. The expression of 1 in an α-amyrin producing yeast strain led to the accumulation of ursolic acid. An enzyme assay using recombinant protein IaAU1 purified from revealed that IaAU1 can catalyze the conversion of ursolic acid to ursolic acid 28--β-D-glucopyranoside. IaAU1 has regiospecificity for catalyzing the 28--glucosylation of ursane-/oleanane-type triterpene acids, as it can also catalyze the conversion of oleanolic acid, hederagenin, and ilexgenin A to their corresponding glycosyl compounds. Moreover, co-expression of 1 and 1 in the α-amyrin-producing yeast strain led to the production of ursolic acid 28--β-D-glucopyranoside, although in relatively low amounts. Our study reveals that 1 and 1 might play a role in the biosynthesis of pentacyclic triterpenoid saponins in and provides insights into the potential application of metabolic engineering to produce ursane-type triterpene glycosides.
是一种在中国南方广泛使用的药用植物。该植物含有乌苏烷型三萜类化合物和三萜皂苷，已知这些成分是其药理活性的原因。此前，对该植物进行了转录组分析，并鉴定了在核心结构α-香树脂醇形成中起重要作用的基因1。然而，与三萜类核心结构后续衍生化相关的基因在很大程度上仍然未知。在此，我们基于转录组数据描述了香树脂醇28-羧化酶IaAO1（命名为IaCYP716A210）和糖基转移酶IaAU1（命名为UGT74AG5）的克隆及功能表征。在产α-香树脂醇的酵母菌株中表达基因1导致了熊果酸的积累。使用从该植物中纯化的重组蛋白IaAU1进行的酶活性测定表明，IaAU1可以催化熊果酸转化为熊果酸28-O-β-D-吡喃葡萄糖苷。IaAU1对催化乌苏烷型/齐墩果烷型三萜酸的28-O-糖基化具有区域特异性，因为它还可以催化齐墩果酸、常春藤皂苷元和平原鹅掌柴苷元A转化为它们相应的糖基化合物。此外，在产α-香树脂醇的酵母菌株中共表达基因1和基因1导致了熊果酸28-O-β-D-吡喃葡萄糖苷的产生，尽管产量相对较低。我们的研究表明，基因1和基因1可能在该植物五环三萜皂苷的生物合成中起作用，并为代谢工程生产乌苏烷型三萜糖苷的潜在应用提供了见解。
