Title : Characterization of glycosyltransferase from rhizobium pusense useful for regioselective production of resveratrol 4'-O-alpha-D-glucoside
Abstract:
Resveratrol is a polyphenolic stilbenoid compound known for its strong anti-oxidative effect, however its bioavailability is limited due to its rapid metabolism and poor water solubility. These drawbacks could be overcome by performing enzymatic structural modification through α-glycosylation. The position of α-glycosylation affects the characteristics of the resveratrol glycoside in which 4′−OH position shows better antiradical properties compared to the 3−OH position. Thus, this study aims to obtain a regioselective enzyme to perform enzymatic synthesis of resveratrol 4′-O-α-glucoside. In this study, we identified and characterized the regioselective glycosyltransferase. First, we carried out screening of regioselective glycosyl transferase useful for resveratrol 4′-O-α-glucoside production and identified Rhizobium pusense JCM 16209T as a potential strain. Two α-glucosidases of R. pusense JCM 16209T (RpG I and RpG II) were identified. Furthermore, we characterized the regioselective glycosyltransferases by cloning and expression in Escherichia coli. RpG I showed strong glycosylation activity toward resveratrol with 4′-selectivity of 98.3 %. The enzyme activity was maximized at pH 8.0 and 50 °C, and enhanced in the presence of Cs+ and Li+ ions. The maximum molar yield of resveratrol 4′-O-α-glucoside from resveratrol reached 41.6 % at 30 min, and the concentration of the product was 2.08 mmol L−1. To the best of our knowledge, there are few reports on microbial glycosyltransferases that are useful for regioselective glycosylation. This study could be the first step toward developing technologies for the precise synthesis of glycosides.
Keywords: resveratrol, enzymatic catalysis, regioselective glycosylation, glycosyltransferase
Audience Take Away:
- Regioselective glycosylation improves resveratrol solubility and antiradical properties Natural resveratrol is commonly obtained from extraction of Japanese knotweed (Fallopia japonica, Polygonaceae) or vine shoots (Vitis vinifera, Vitaceae). Resveratrol has been studied for its potential as antioxidant or anticancer agent. Despite the potentials, its application is limited due to instability against oxidation and its low bioavailability related to its low water solubility. For example, it was found that 75% of the trans-resveratrol was excreted in urine while the remaining 25% was quickly metabolized inducing a bioavailability nearly zero. Structural modification of resveratrol by O-glycosylation is a promising approach to ameliorate resveratrol bioavailability. Bounding sugars to resveratrol through glycosylation leads to a higher water solubility and bioavailability and protects it against oxidation. The structure of resveratrol glycosides determine the degree of the water solubility as well as its antiradical properties. The α-glycosides of resveratrol showed new surfactant properties that are not found in 3-O-β-glucoside (piceid), the most common form in which resveratrol exists in plants. As a result, the water solubility of these α-glycosides is 65-fold higher than that of resveratrol. Moreover, the glycosylation position in 4′−OH was shown to be the best position for the glycosylation to maintain the highest antiradical properties compared to the 3−OH position. Thus, regioselective glycosylation performed in this study could serve as reference to improve resveratrol solubility while maintaining its antiradical properties.
- Regioselective glycodiversification of polyphenol compounds
This research contributes to the effort to produce glycodiversified polyphenol derivatives with emphasize on regioselective production. Glycosylation has been developed as a tool for generating biologically potent and novel glycoside compounds with potential application in nutraceuticals, cosmetics, or pharmaceutical industries.The regioselective glucosidase was demonstrated to be highly regioselective over varying polyphenolic compounds other than reseveratrol i.e. ferulic acid, 6-gingerol, tetrahydrocurcumin, naringenin, and caffeic acid with regioselectivity (%) of 100, 100, 100, 91.8, and 75.6, respectively. The enzyme identified and characterized in this research could be useful to perform regioselective glycosylation with 4′-selectivity for polyphenol compounds.
