Effect of Uridine on Hepatic Galactose-1-Phosphate Uridyltransferase

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Abstract
Uridine sugar nucleotides are important intermediates in galactose metabolism and may play a role in the long-term galactose toxicity in human galactose-1-phosphate uridyltransferase deficiency galactosemia. Since administration of uridine, a precursor of uridine necleotides, has been considered as a therapeutic measure, we have investigated the effects of this compound on the activity of rat hepatic transferase. Urdine has been found to be an inhibitor of the enzyme in in vitro studies and to cause an increase in galactose-1-phosphate in liver perfused with galactose which is consistent with physiologic inhibition of the enzyme. Uridine is a partial linear competitive inhibitor of UDP-glucose and an uncompetitive inhibitor of galactose-1-phosphate. These findings suggest caution should be applied in giving the compound to subjects with genetically limited transferase activity because of the possiblity of inhibiting the small amount of residual enzyme.