Effect of Some Nucleotides on the Regulation of Glycosaminoglycan Biosynthesis
- 1 January 1976
- journal article
- Published by Taylor & Francis in Connective Tissue Research
- Vol. 4 (4) , 247-254
- https://doi.org/10.3109/03008207609152227
Abstract
The effect of some nucleotides on UDP-glucose dehydrogenase (EC. 1.1.1.22) and UDP-glucose 4'-epimerase (EC 5.1.3.2) extracted from epiphysial-plate cartilage of newborn pigs was investigated. UDP-xylose acts as a co-operative allosteric inhibitor of UDP-glucose dehydrogenase, whereas it does not inhibit UDP-glucose 4'-epimerase activity: the inhibition of UDP-glucose dehydrogenase results in an increase of UDP-galactose synthesis, in agreement with the equilibrium constant of UDP-glucose 4'-epimerase reaction. Because of the presence of UDP-glucose 4'-epimerase activity in the enzyme extract, the addition of UDP-galactose induces an increase in reaction rate of UDP-glucose dehydrogenase. NADH inhibits both UDP-glucose dehydrogenase and UDP-glucose 4'-epimerase activities: in the presence of non-saturating NAD concentrations, NADH acts as a co-operative allosteric inhibitor of both enzymes. The inhibitory effect of NADH seems to be strikingly correlated with the value of NAD/NADH ratio and pH. In any case, the percentage inhibition of UDP-glucose 4'-epimerase, under the same experimental conditions, is always higher than that of UDP-glucose dehydrogenase.Keywords
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