A New Triterpenoid Glucoside from a Novel Acidic Glycosylation of Ganoderic Acid A via Recombinant Glycosyltransferase of Bacillus subtilis

Molecules

Tzi-Yuan Wang¹  Yu-Han Kao²  Te-Sheng Chang²  Chien-Min Chiang³  Jiumn-Yih Wu⁴  Yu-Wei Wu⁵ 

[1] Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan;Department of Biological Sciences and Technology, National University of Tainan, Tainan 70005, Taiwan;Department of Biotechnology, Chia Nan University of Pharmacy and Science, No. 60, Sec. 1, Erh-Jen Rd., Jen-Te District, Tainan 71710, Taiwan;Department of Food Science, National Quemoy University, Kinmen County 892, Taiwan;Graduate Institute of Biomedical Informatics, College of Medical Science and Technology, Taipei Medical University, Taipei 106, Taiwan;

关键词: ganoderic acid A;    glucosyltransferase;    acidic;    Bacillus subtilis;    triterpenoid;   

DOI  :  10.3390/molecules24193457

来源: DOAJ

【 摘 要 】

Ganoderic acid A (GAA) is a bioactive triterpenoid isolated from the medicinal fungus Ganoderma lucidum. Our previous study showed that the Bacillus subtilis ATCC (American type culture collection) 6633 strain could biotransform GAA into compound (1), GAA-15-O-β-glucoside, and compound (2). Even though we identified two glycosyltransferases (GT) to catalyze the synthesis of GAA-15-O-β-glucoside, the chemical structure of compound (2) and its corresponding enzyme remain elusive. In the present study, we identified BsGT110, a GT from the same B. subtilis strain, for the biotransformation of GAA into compound (2) through acidic glycosylation. BsGT110 showed an optimal glycosylation activity toward GAA at pH 6 but lost most of its activity at pH 8. Through a scaled-up production, compound (2) was successfully isolated using preparative high-performance liquid chromatography and identified to be a new triterpenoid glucoside (GAA-26-O-β-glucoside) by mass and nuclear magnetic resonance spectroscopy. The results of kinetic experiments showed that the turnover number (k_cat) of BsGT110 toward GAA at pH 6 (k_cat = 11.2 min⁻¹) was 3-fold higher than that at pH 7 (k_cat = 3.8 min⁻¹), indicating that the glycosylation activity of BsGT110 toward GAA was more active at acidic pH 6. In short, we determined that BsGT110 is a unique GT that plays a role in the glycosylation of triterpenoid at the C-26 position under acidic conditions, but loses most of this activity under alkaline ones, suggesting that acidic solutions may enhance the catalytic activity of this and similar types of GTs toward triterpenoids.

【 授权许可】

Unknown