The enzymatic transfer of hydrogen. V. The reaction catalyzed by glucose dehydrogenase.

Previous studies with the aid of deuterium as a tracer have shown that alcohol dehydrogenase (1)) lactic dehydrogenase (2)) malic dehydrogenase (3)) and a /?-hydroxysteroid dehydrogenase (4) all catalyze the direct transfer of hydrogen between their respective substrates and the para position of the nicotinamide ring of DPN.’ This hydrogen transfer was also shown to be stereospecific for the DPN. Alcohol, lactic, and malic dehydrogenases all cause hydrogen transfer to and from the same side (designated a)’ of the nicotinamide ring, whereas the p-hydroxysteroid dehydrogenase causes transfer to and from the opposite or “p” side of the ring. The present paper describes an extension of these studies to glucose dehydrogenase, and presents evidence that the reaction catalyzed by this enzyme involves a direct transfer of hydrogen from carbon 1 of glucose to the j3 side of the nicotinamide ring of DPN.