Catalyzes the NAD(P)(+)-dependent oxidation of D-glucose to D-gluconate via gluconolactone. Is also significantly active with D-galactose as substrate, but not with D-xylose, L-arabinose, D-ribose, D-mannose, D-allose, D-glucosamine, 2-deoxy-D-glucose, or glucose-6-phosphate. Can utilize both NAD(+) and NADP(+) as electron acceptor, with a marked preference for NADP(+) (20-fold higher activity). Physiologically, may be involved in the degradation of both glucose and galactose through a non-phosphorylative variant of the Entner-Doudoroff pathway. D-glucose + NADP(+) = D-glucono-1,5-lactone + H(+) + NADPH D-galactose + NADP(+) = D-galactono-1,5-lactone + H(+) + NADPH Zn(2+) is of critical importance for the stability of the enzyme. Optimum pH is 6.5 for the oxidation of D-glucose by NADP(+). At the physiological pH of 4.6 found in the cytoplasm of Picrophilus cells, the enzyme shows merely 10% of its maximal activity. Optimum temperature is 55 degrees Celsius for the oxidation of D-glucose by NADP(+). Homotetramer. Belongs to the zinc-containing alcohol dehydrogenase family. Glucose 1-dehydrogenase subfamily.