Uridine Diphosphate d -Glucose Dehydrogenase of Aerobacter aerogenes

Abstract

Uridine diphosphate d -glucose dehydrogenase (EC 1.1.1.22) from Aerobacter aerogenes has been partially purified and its properties have been investigated. The molecular weight of the enzyme is between 70,000 and 100,000. Uridine diphosphate d -glucose is a substrate; the diphosphoglucose derivatives of adenosine, cytidine, guanosine, and thymidine are not substrates. Nicotinamide adenine dinucleotide (NAD), but not nicotinamide adenine dinucleotide phosphate, is active as hydrogen acceptor. The p H optimum is between 9.4 and 9.7; the K m is 0.6 m m for uridine diphosphate d -glucose and 0.06 m m for NAD. Inhibition of the enzyme by uridine diphosphate d -xylose is noncooperative and of mixed type; the K i is 0.08 m m . Thus, uridine diphosphate d -glucose dehydrogenase from A. aerogenes differs from the enzyme from mammalian liver, higher plants, and Cryptococcus laurentii , in which uridine diphosphate d -xylose functions as a cooperative, allosteric feedback inhibitor.