Localization and Characteristics of Hexose 6-Phosphate Dehydrogenase (Glucose Dehydrogenase)

Abstract The autosomally inherited glucose-6-P dehydrogenase of liver has now been found to catalyze the oxidation not only of galactose-6-P, as previously reported, but also glucose and 2-deoxyglucose-6-P. The enzyme was localized in the microsomal fraction of liver. The pH optimum of the enzyme was dependent not only upon the hexose used as substrate, but also upon the substrate concentration. The Michaelis constant was very pH-sensitive and ranged from less than 0.005 mm for galactose-6-P with NAD as hydrogen acceptor to over 4000 mm when glucose served as substrate and NADP as the hydrogen acceptor. Purification and electrophoretic studies indicate that the dehydrogenase activities with glucose, glucose-6-P, 2-deoxyglucose-6-P, and galactose-6-P as substrate are properties of the same enzyme.