Antimicrobial mechanism of theaflavins: They target 1-deoxy-D-xylulose 5-phosphate reductoisomerase, the key enzyme of the MEP terpenoid biosynthetic pathway.

Xian Hui,Wen-Yun Gao,Shao-Qing Yang,Qiao Yue,Dan-Dan Zhang,Heng Li

doi:10.1038/srep38945

Abstract

1-Deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) is the first committed enzyme in the 2-methyl-D-erythritol 4-phosphate (MEP) terpenoid biosynthetic pathway and is also a validated antimicrobial target. Theaflavins, which are polyphenolic compounds isolated from fermented tea, possess a wide range of pharmacological activities, especially an antibacterial effect, but little has been reported on their modes of antimicrobial action. To uncover the antibacterial mechanism of theaflavins and to seek new DXR inhibitors from natural sources, the DXR inhibitory activity of theaflavins were investigated in this study. The results show that all four theaflavin compounds could specifically suppress the activity of DXR, with theaflavin displaying the lowest effect against DXR (IC50 162.1 μM) and theaflavin-3,3′-digallate exhibiting the highest (IC50 14.9 μM). Moreover, determination of inhibition kinetics of the theaflavins demonstrates that they are non-competitive inhibitors of DXR against 1-deoxy-D-xylulose 5-phosphate (DXP) and un-competitive inhibitors with respect to NADPH. The possible interactions between DXR and the theaflavins were simulated via docking experiments.

Highlights

Up to date, 2-methyl-D-erythritol 4-phosphate (MEP) pathway for the biosynthesis of terpenoids has been found and established[1]
We evaluated the reliability of the HPLC method in the measurement of D-xylulose 5-phosphate reductoisomerase (DXR) inhibitory activity of the theaflavins
Fosmidomycin, hitherto the most potent inhibitor of DXR, has drawbacks such as poor bioavailability, short plasma half-life (~1 h), and metabolic liability, which have precluded its in vivo application as a DXR inhibitor[1]

Summary

Introduction

2-methyl-D-erythritol 4-phosphate (MEP) pathway for the biosynthesis of terpenoids has been found and established[1]. Much research has been performed to seek its inhibitors, resulting in the discovery of fosmidomycin (3, Fig. 1), a phosphonate compound previously isolated from Streptomyces lavendulae and its structural analogue FR900098 (4). These two highly hydrophilic compounds are potent DXR inhibitors, but show strong antibacterial effects as well[3]. Theaflavin (TF), theaflavin-3-gallate (TF3G), theaflavin-3′-gallate (TF3′G), and theaflavin-3,3′-digallate (TF3,3′G) (Fig. 2) have been characterized. Research has shown they exhibit a broad spectrum of physiological effects, such as www.nature.com/scientificreports/ Figure 1. The aims of the study are to disclose the possible antibacterial mechanism of the theaflavins and to seek new DXR inhibitors

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Conclusion