AUTHOR=Ali Mohamed Yassin , Chang Qing , Yan Quande , Qian Zheng , Guo Xiang , Thow Kieran , Wu Jinhong , Zhang Yong , Feng Yan TITLE=Highly Efficient Biosynthesis of Glycyrrhetinic Acid Glucosides by Coupling of Microbial Glycosyltransferase to Plant Sucrose Synthase JOURNAL=Frontiers in Bioengineering and Biotechnology VOLUME=Volume 9 - 2021 YEAR=2021 URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2021.645079 DOI=10.3389/fbioe.2021.645079 ISSN=2296-4185 ABSTRACT=Glycyrrhetinic acid (GA) glycoside derivatives are important bioactive pentacyclic triterpenoid compounds. Glycyrrhetinic acid is the most important Glycyrrhiza uralensis component due to its potent anti-inflammatory activity and extensive use in the pharmaceutical and cosmetics industries. UDP-glycosyltransferases (UGTs) catalyze various natural products' glycosylation using Glycyrrhetinic acid (GA) is a principal bioactive pentacyclic triterpenoid from Glycyrrhiza uralensis. UDP-dependent glycosyltransferases (UGTs) have been widely used to catalyze glycosylation of diverse nature products for developing potential therapeutic compounds. In this study, we have characterized a UGT109A3 from Bacillus subtilis, which can glycosylate both the free C3 hydroxyl and C30 carboxyl groups of GA to yield a unique 3, 30-O-β-D-diglucoside-GA. By coupling the microbial UGT109A3 to plant sucrose synthase (SUS), GA-diglucoside could be biosynthesized in an efficient and economical way. With a fed-batch glycosylation, a large scale of GA-glucoside (4.98 g/L, 6.26 mM in 8 hours) could be enzymatically transformed from GA. The obtained GA-diglucoside showed a significant water solubility improvement around 3.4×103 fold compared with that of the parent GA (29 µM). Moreover, it also exhibited dose-dependent cytotoxic towards human colon carcinoma Caco-2 cell line according to MTT assay, having an IC50 at 160 µM. This study not only builds up an efficient platform for producing GA-glucosides, and also is valuable for further biosynthesis of other complex glycosylated natural products.