Ursolic Acid Targets Glucosyltransferase and Inhibits Its Activity to Prevent Streptococcus mutans Biofilm Formation

Yucui Liu; Yanxin Huang; Cong Fan; Zhongmei Chi; Miao Bai; Luguo Sun; Li Yang; Chunlei Yu; Zhenbo Song; Xiaoguang Yang; Jingwen Yi; Shuyue Wang; Lei Liu; Guannan Wang; Lihua Zheng

doi:10.3389/fmicb.2021.743305

Ursolic Acid Targets Glucosyltransferase and Inhibits Its Activity to Prevent Streptococcus mutans Biofilm Formation

Front Microbiol. 2021 Sep 27:12:743305. doi: 10.3389/fmicb.2021.743305. eCollection 2021.

Authors

Yucui Liu^{1

2}, Yanxin Huang³, Cong Fan^{1

4}, Zhongmei Chi⁵, Miao Bai¹, Luguo Sun³, Li Yang⁵, Chunlei Yu¹, Zhenbo Song¹, Xiaoguang Yang^{1

3}, Jingwen Yi^{1

3}, Shuyue Wang¹, Lei Liu¹, Guannan Wang¹, Lihua Zheng¹

Affiliations

¹ National Engineering Laboratory for Druggable Gene and Protein Screening, Northeast Normal University, Changchun, China.
² State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China.
³ NMPA Key Laboratory for Quality Control of Cell and Gene Therapy Medicine Products, Northeast Normal University, Changchun, China.
⁴ Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Department of Medical Research Center, Sun Yat-Sen Memorial Hospital, Guangzhou, China.
⁵ Faculty of Chemistry, Northeast Normal University, Changchun, China.

Abstract

Streptococcus mutans (S. mutans), the prime pathogen of dental caries, can secrete glucosyltransferases (GTFs) to synthesize extracellular polysaccharides (EPSs), which are the virulence determinants of cariogenic biofilms. Ursolic acid, a type of pentacyclic triterpene natural compound, has shown potential antibiofilm effects on S. mutans. To investigate the mechanisms of ursolic acid-mediated inhibition of S. mutans biofilm formation, we first demonstrated that ursolic acid could decrease the viability and structural integrity of biofilms, as evidenced by XTT, crystal violet, and live/dead staining assays. Then, we further revealed that ursolic acid could compete with the inherent substrate to occupy the catalytic center of GTFs to inhibit EPS formation, and this was confirmed by GTF activity assays, computer simulations, site-directed mutagenesis, and capillary electrophoresis (CE). In conclusion, ursolic acid can decrease bacterial viability and prevent S. mutans biofilm formation by binding and inhibiting the activity of GTFs.

Keywords: biofilms; extracellular polysaccharides; glucosyltransferases; mechanism; ursolic acid.