K. Stephan, A. D. Todd, Rosalind Williams
Oct 1, 2001
Citations
0
Influential Citations
0
Citations
Journal
The Journal of Physiology
Abstract
D-Glucuronolactone is known to be an intermediate in mammalian ascorbic acid synthesis, and in all animals, including those unable to synthesize the vitamin, it is also converted to L-xylulose and then degraded into products which enter the common metabolic pool. A competing pathway has now been found whereby D-glucuronolactone is oxidized by a DPN-dependent dehydrogenase present in liver, and to a lesser extent in kidney and testis, to D-glucosaccharic acid, which is excreted in the urine and was detected by its specific inhibitory effect upon fl-glucuronidase and also isolated. Compounds such as barbiturates which elevate the excretion of D-glucuronic acid and L-ascorbic acid have been found to inhibit the oxidative enzyme. The activity of glucuronolactone dehydrogenase is virtually nil in infant ratand mouse-liver preparations and is low in human foetal liver. This decreased production of a natural fl-glucuronidase inhibitor may aggravate the increased bilirubin load in the new-born where the detoxicating mechanism of conjugation with glucuronic acid is also deficient (Zuelzer & Brown, 1961). The excretion of saccharic acid by women increased during pregnancy, returning to normal within a few days of parturition. In pregnant mouse liver there is an increase in the glucuronolactone dehydrogenase activity. After ingestion of glucuronolactone by man, one fifth of the dose appears in the urine as saccharic acid within 48 hr.