A Novel Glycoside Hydrolase Family 5 β-1,3-1,6-Endoglucanase from Saccharophagus degradans 2-40T and Its Transglycosylase Activity

In this study, we characterized Gly5M, originating from a marine bacterium, as a novel beta-1,3-1,6-endoglucanase in glycoside hydrolase family 5 (GH5) in the Carbohydrate-Active enZyme database. The gly5M gene encodes Gly5M, a newly characterized enzyme from GH5 subfamily 47 (GH5_47) in Saccharophagus degradans 2-40(T). The gly5M gene was cloned and overexpressed in Escherichia coli. Through analysis of the enzymatic reaction products by thin-layer chromatography, high-performance liquid chromatography, and matrix-assisted laser desorption ionization-tandem time of flight mass spectrometry, Gly5M was identified as a novel beta-1,3-endoglucanase (EC 3.2.1.39) and bacterial beta-1,6-glucanase (EC 3.2.1.75) in GH5. The beta-1,3-endoglucanase and beta-1,6-endoglucanase activities were detected by using laminarin (a beta-1,3-glucan with beta-1,6-glycosidic linkages derived from brown macroalgae) and pustulan (a beta-1,6-glucan derived from fungal cell walls) as the substrates, respectively. This enzyme also showed transglycosylase activity toward beta-1,3-oligosaccharides when laminarioligosaccharides were used as the substrates. Since laminarin is the major form of glucan storage in brown macroalgae, Gly5M could be used to produce glucose and laminarioligosaccharides, using brown macroalgae, for industrial purposes. IMPORTANCE In this study, we have discovered a novel beta-1,3-1,6-endoglucanase with a unique transglycosylase activity, namely, Gly5M, from a marine bacterium, Saccharophagus degradans 2-40(T). Gly5M was identified as the newly found beta-1,3-endoglucanase and bacterial beta-1,6-glucanase in GH5. Gly5M is capable of cleaving glycosidic linkages of both beta-1,3-glucans and beta-1,6-glucans. Gly5M also possesses a transglycosylase activity toward beta-1,3-oligosacchrides. Due to the broad specificity of Gly5M, this enzyme can be used to produce glucose or high-value beta-1,3-and/or beta-1,6-oligosaccharides.