Interaction of uridine diphosphate glucose with calf liver uridine diphosphate glucose dehydrogenase. Significance of hydroxyl groups at C-3, C-4 and C-6 of hexosyl residue.

Analogs of uridine diphosphate glucose (UDPGlc) with a modified hexosyl residue which contained a deoxy-unit at C-3 or C-4 were tested as substrates of calf liver UDPGlc dehydrogenase (EC 1.1.1.22). The 3-deoxyglucose derivative was found not to serve as a substrate for the enzyme whereas the 4-deoxyglucose analog was able to participate in the reaction. The apparent Km of the latter was 5.3 times that of UDPGlc and the relative V was 0.04. The reaction product was identified as uridine diphosphate deoxyhexuronic acid. UDP-deoxyhexoses were non-competitive inhibitors of UDPGlc enzymic oxidation, inhibition increased in the sequence: 2-deoxy-less than 3-and 6-deoxy-less than 4-deoxyglucose derivative. The significance of different HO-groups in hexosyl residue for interaction of UDPGlc with the enzyme is discussed.