An inverting ß-1,2-mannosidase belonging to glycoside hydrolase family 130 from Dyadobacter fermentans.

The glycoside hydrolase family (GH) 130 is composed of inverting phosphorylases that catalyze reversible phosphorolysis of ß-D-mannosides. Here we report a glycoside hydrolase as a new member of GH130. Dfer_3176 from Dyadobacter fermentans showed no synthetic activity using α-D-mannose 1-phosphate but it released α-D-mannose from ß-1,2-mannooligosaccharides with an inversion of the anomeric configuration, indicating that Dfer_3176 is a ß-1,2-mannosidase. Mutational analysis indicated that two glutamic acid residues are critical for the hydrolysis of ß-1,2-mannotriose. The two residues are not conserved among GH130 phosphorylases and are predicted to assist the nucleophilic attack of a water molecule in the hydrolysis of the ß-D-mannosidic bond.