β-1,3-Glucan-degrading enzymes are widely used in fields such as food processing, plant protection, and breweries. In this work, we identified a glycoside hydrolase (GH) family 157 endo-β-1,3-glucanase (BsGlc157A) from Bacteroides sp. M27 and characterized its biochemical properties, structural model, and antifungal activity. Enzymological characterization indicated that BsGlc157A performs its optimal catalytic activity at pH 6.0 and 40 °C. BsGlc157A adopted the classic (β/α)8 TIM-barrel structure. Two catalytic residues, the nucleophile (Glu215) and the proton donor (Glu123), were confirmed via structural modeling and site-directed mutagenesis. Moreover, BsGlc157A hydrolyzed curdlan into a series of oligosaccharides with polymerization degrees 2–5 and exhibited inhibitory effects on the hyphal growth of typical fruit pathogenic fungi (Monilinia fructicola, Alternaria alternata, and Colletotrichum gloeosporioides), thereby illustrating effective biocontrol activity. These results revealed the catalytic properties and the application potential of GH family 157 β-1,3-glucanase, thus providing valuable biochemistry information about the group of carbohydrate-active enzymes.
β-1,3-Glucanases have prospective applications in areas such as functional oligosaccharide preparation, plant protection, and breweries. In this study, a glycoside hydrolase (GH) family 17 β-1,3-glucanase (BbGlc17A) from Bacteroidetes bacterium from a microbial mat metagenome from the Great Salt Lake was identified. BbGlc17A catalyzed the hydrolytic conversion of laminarin into β-glucooligosaccharides with polymerization degrees of 3–8. The optimal catalytic conditions of BbGlc17A were pH 6.5 and 30 °C. In addition to its hydrolytic activity, BbGlc17A also exhibited transglycosidase activities, involving catalysis of the formation of new β-1,6-glycosidic bonds. BbGlc17A exhibits the classic (β/α)8 TIM-barrel structure and possesses an elongated catalytic groove, distinguishing it from other typical β-1,3-glucanases, which promote the forward direction of the transglycoside reaction. This effectively highlights the potential of the enzyme to convert β-1,3-glucan into mixed functional oligosaccharides. These results reveal the catalytic properties and the application potential of the GH family 17 β-1,3-glucanase and provide valuable information about the group of carbohydrate-active enzymes in biochemistry.
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