Aldose sugar dehydrogenase with broad substrate specificity. The physiological substrate is unknown. Can oxidize glucose to gluconolactone. Can also utilize D-arabinose, L-arabinose and 2-deoxy-glucose. Has higher activity towards oligomeric sugars, such as maltose, maltotriose or cellobiose. It may function to input sugar-derived electrons into the respiratory network. Binds 2 calcium ions per monomer. Monomer. Belongs to the PQQ oxidoreductase GdhB family.