Catalyzes the oxidation of various aldopyranoses and disaccharides on carbon-2 to the corresponding 2-keto sugars concomitant with the reduction of O(2) to H(2)O(2). The preferred substrate is D-glucose which is converted to 2-dehydro-D-glucose. Acts also on D-xylose, L-sorbose, D-galactose and 1,5-anhydroglucitol, a diagnostic marker of diabetes mellitus. D-glucose + O2 = 2-dehydro-D-glucose + H2O2 Binds 1 FAD covalently per subunit. Optimum pH is 7.5-8.0. Active from pH 6 to 10. Stable from pH 5 to 11. Optimum temperature is 50 degrees Celsius. Active from 30 to 65 degrees Celsius. Thermostable for 30 minutes up to 55 degrees Celsius. Homotetramer. Belongs to the GMC oxidoreductase family.