Uridine Diphosphate Glucose Dehydrogenase

J-Hydroxyuridine cliphosphateglucose was prepared enzymatically and 5,Bdihydrouridine diphosphate glucose was prepared by the catalytic reduction of UDP-glucose.The effectiveness of these cofactor analogues as substrates for UDP-glucose dehydrogenase was determined.The rate of oxidation of 5-hydroxyuridine diphosphate glucose was onesixth that of UDP-glucose at pH 8.7 and one-half that of UDP-glucose at pH 7.0.This behavior is related to the relatively low pKa value of the analogue.Dihydrouridine diphosphate glucose was oxidized at rates which were almost identical with those observed with UDP-glucose at various pH values.5-Hydrozyuridine diphosphate glucose inhibited UDPglucose oxidation in a manner suggesting that the analogue interferes with the NADf binding site of the enzyme.The undissociated form of the analogue was the more effective inhibitor of UDP-glucose oxidation.