Regulation of ascorbic acid and of xylulose synthesis in rat-liver extracts. The effect of alloxan-diabetes on the glucuronic acid pathway.

1. The synthesis of l-ascorbic acid and of l-xylulose from d-glucuronolactone, d-glucuronate, l-gulonate and l-gulonolactone has been studied with liver extracts from normal and alloxan-diabetic rats. 2. In diabetic animals the synthesis of ascorbic acid is impaired, and more from glucuronolactone and glucuronate than from gulonate and gulonolactone, whereas the formation of xylulose from gulonate and gulonolactone is enhanced. These changes are reversed by insulin therapy. 3. The activity of the NAD-linked gulonate dehydrogenase is enhanced during diabetes.