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.
Research Article|February 01 1975
Interactions of urdine diphosphate glucose dehydrogenase with the inhibitor urdine diphosphate xylose
P A Gainey;
Biochem J (1975) 145 (2): 129-134.
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P A Gainey, C F Phelps; Interactions of urdine diphosphate glucose dehydrogenase with the inhibitor urdine diphosphate xylose. Biochem J 1 February 1975; 145 (2): 129–134. doi: https://doi.org/10.1042/bj1450129
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