Characterization of regioselective glycosyltransferase of Rhizobium pusense JCM 16209T useful for resveratrol 4'-O-α-d-glucoside production

Exploring gingerol glucosides with enhanced anti-inflammatory activity through a newly identified α-glucosidase (ArG) from Agrobacterium radiobacter DSM 30147

Gingerols are phenolic biomedical compounds found in ginger (Zingiber officinale) whose low aqueous solubility limits their medical application. To improve their solubility and produce novel glucosides, an α-glucosidase (glycoside hydrolase) from Agrobacterium radiobacter DSM 30147 (ArG) was subcloned, expressed, purified, and then confirmed to have additional α-glycosyltransferase activity. After optimization, the ArG could glycosylate gingerols into three mono-glucosides based on the length of their acyl side chains. Compound 1 yielded 63.0 %, compound 2 yielded 26.9 %, and compound 3 yielded 4.37 %. The production yield of the gingerol glucosides optimally increased in 50 mM phosphate buffer (pH 6) with 50 % (w/v) maltose and 1000 mM Li+ at 40 °C for an 24-h incubation. The structures of purified compound 1 and compound 2 were determined as 6-gingerol-5-O-α-glucoside (1) and novel 8-gingerol-5-O-α-glucoside (2), respectively, using nucleic magnetic resonance and mass spectral analyses. The aqueous solubility of the gingerol glucosides was greatly improved. Further assays showed that, unusually, 6-gingerol-5-O-α-glucoside had 10-fold higher anti-inflammatory activity (IC50 value of 15.3 ± 0.5 μM) than 6-gingerol, while the novel 8-gingerol-5-O-α-glucoside retained 42.7 % activity (IC50 value of 106 ± 4 μM) compared with 8-gingerol. The new α-glucosidase (ArG) was confirmed to have acidic α-glycosyltransferase activity and could be applied in the production of α-glycosyl derivatives. The 6-gingerol-5-O-α-glucoside can be applied as a clinical drug for anti-inflammatory activity.

A mutant GH3 family β-glucosidase from Oenococcus oeni exhibits superior adaptation to wine stresses and potential for improving wine aroma and phenolic profiles

In this study, we conducted a comprehensive investigation into a GH3 family β-glucosidase (BGL) from the wild-type strain of Oenococcus oeni and its mutated counterpart from the acid-tolerant mutant strain. Our analysis revealed the mutant BGL's remarkable capacity to adapt to wine-related stress conditions, including heightened tolerance to low pH, elevated ethanol concentrations, and metal ions. Additionally, the mutant BGL exhibited superior hydrolytic activity towards various substrates. Through de novo modeling, we identified specific amino acid mutations responsible for its resilience to low pH and high ethanol environments. In simulated wine conditions, the mutant BGL outperformed both wild-type and commercial BGLs, efficiently releasing terpene and phenolic aglycones from glycosides in wine grapes. These findings not only expand our understanding of O. oeni BGLs but also highlight their potential in enhancing wine production. The mutant BGL's enhanced adaptation to wine stress conditions opens promising avenue for improving wine quality and flavor.

Fusarium sporotrichioides Produces Two HT-2-α-Glucosides on Rice

Fusarium is a genus that mostly consists of plant pathogenic fungi which are able to produce a broad range of toxic secondary metabolites. In this study, we focus on a type A trichothecene-producing isolate (15-39) of Fusarium sporotrichioides from Lower Austria. We assessed the secondary metabolite profile and optimized the toxin production conditions on autoclaved rice and found that in addition to large amounts of T-2 and HT-2 toxins, this strain was able to produce HT-2-glucoside. The optimal conditions for the production of T-2 toxin, HT-2 toxin, and HT-2-glucoside on autoclaved rice were incubation at 12 °C under constant light for four weeks, darkness at 30 °C for two weeks, and constant light for three weeks at 20 °C, respectively. The HT-2-glucoside was purified, and the structure elucidation by NMR revealed a mixture of two alpha-glucosides, presumably HT-2-3-O-alpha-glucoside and HT-2-4-O-alpha-glucoside. The efforts to separate the two compounds by HPLC were unsuccessful. No hydrolysis was observed with two the alpha-glucosidases or with human salivary amylase and Saccharomyces cerevisiae maltase. We propose that the two HT-2-alpha-glucosides are not formed by a glucosyltransferase as they are in plants, but by a trans-glycosylating alpha-glucosidase expressed by the fungus on the starch-containing rice medium.

Utilization of glycosyltransferases as a seamless tool for synthesis and modification of the oligosaccharides-A review

Glycosyltransferases (GTs) catalyze the transfer of active monosaccharide donors to carbohydrates to create a wide range of oligosaccharide structures. GTs display strong regioselectivity and stereoselectivity in producing glycosidic bonds, making them extremely valuable in the in vitro synthesis of oligosaccharides. The synthesis of oligosaccharides by GTs often gives high yields; however, the enzyme activity may experience product inhibition. Additionally, the higher cost of nucleotide sugars limits the usage of GTs for oligosaccharide synthesis. In this review, we comprehensively discussed the structure and mechanism of GTs based on recent literature and the CAZY website data. To provide innovative ideas for the functional studies of GTs, we summarized several remarkable characteristics of GTs, including folding, substrate specificity, regioselectivity, donor sugar nucleotides, catalytic reversibility, and differences between GTs and GHs. In particular, we highlighted the recent advancements in multi-enzyme cascade reactions and co-immobilization of GTs, focusing on overcoming problems with product inhibition and cost issues. Finally, we presented various types of GT that have been successfully used for oligosaccharide synthesis. We concluded that there is still an opportunity for improvement in enzymatically produced oligosaccharide yield, and future research should focus on improving the yield and reducing the production cost.