Purification and Properties of a Nicotinamide Adenine Dinucleotide Phosphate-linked Aldohexose Dehydrogenase from Gluconobacter cerinus

A soluble NADP-linked aldohexose dehydrogenase has been isolated and purified about 100-fold from extracts of Gluconobacter cerinus cells. The enzyme catalyzes the oxidation of d-glucose, d-mannose, 2-deoxy-d-glucose, and 2-amino-2-deoxy-d-mannose with apparent Km values at pH 8.0 of 5.3 x 10-3 m, 1.8 x 10-3 m, 3.9 x 10-2 m, and 2.9 x 10-2 m, respectively. Other aldohexoses or aldopentoses examined were inert either as substrates or as inhibitors. The product of the enzymatic oxidation of d-glucose was characterized as the corresponding hexonic acid-δ-lactone. Reversibility of the reaction has been shown by the identification of d-glucose as the product of NADPH oxidation in the presence of d-glucono-δ-lactone. The enzyme shows high specificity for NADP+ (Km = 1.2 x 10-5 m) and NADPH (Ki = 3.8 x 10-5 m).