title: Interactions of urdine diphosphate glucose dehydrogenase with the inhibitor urdine diphosphate xylose.
abstract: 1. UDP-xylose and UDP-glucose both bind to UDP-glucose dehydrogenase in the absence of NAD+, causing an enhancement of protein fluorescence. 2. The binding of UDP-xylose is pH-dependent, tighter binding being observed at pH8.2 than at pH8.7. 3. At low protein concentrations sigmiodal profiles of fluorescence enhancement are obtained on titration of the enzyme with UDP-xylose. As the protein concentration is increased the titration profiles become progressively more hypebolic in shape. 4. The markedly different titration profiles obtained on titrating enzyme and the enzyme-NAD+ complex with UDP-xylose suggests a conformational difference between these two species 5. NAD+ lowere the apparent affinity of the enzyme for UDP-xylose. 6. There is no change in the apparent moleculare weight of UDP-glucose dehydrogenase on binging UDP-xylose. 7. Protein modification by either diethyl pyrocarbonate or 5, 5'-dithiobis-(2-nitrobenzoate) does not "desensitize" the enzyme with respect to the inhibition by UDP-xylose. 8. UDP-xylose lowers the affinity of the enzyme for NADG. 9. It is suggested that UDP-xylose is acting as a substrate analogue of UDP-glucose and causes protein-conformational changes on binding to the enzyme.
mesh_terms: D000429:Alcohol Oxidoreductases / Q000037:antagonists & inhibitors*; D004047:Diethyl Pyrocarbonate; D004228:Dithionitrobenzoic Acid; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D008968:Molecular Conformation; D008970:Molecular Weight; D009243:NAD; D011485:Protein Binding; D011487:Protein Conformation; D014532:Uridine Diphosphate Glucose; D014533:Uridine Diphosphate Glucose Dehydrogenase / Q000037:antagonists & inhibitors*; D014539:Uridine Diphosphate Sugars / Q000494:pharmacology*; D014540:Uridine Diphosphate Xylose / Q000494:pharmacology*
chemical_list: D014539:Uridine Diphosphate Sugars; D009243:NAD; D014540:Uridine Diphosphate Xylose; D004228:Dithionitrobenzoic Acid; D000429:Alcohol Oxidoreductases; D014533:Uridine Diphosphate Glucose Dehydrogenase; D004047:Diethyl Pyrocarbonate; D014532:Uridine Diphosphate Glucose