The primary objective of our research remains that of acquiring a knowledge of the mechanism of the UDP-glucose dehydrogenase reaction, and its biological regulation. Such knowledge could be of fundamental importance in the treatment of diseases, such as neonatal jaundice, which arise from the failure of conjugation of toxic substances via UDP-glucuronic acid, the reaction product. Our studies on the mechanism of the reaction will use pure UDP-glucose dehydrogenase from beef liver. Measurements of the binding of labeled substrates, such as UDP-glucose or NAD ion, and products, such as UDP-glucuronic acid or NADH, will be carried out with the aid of radioactively labeled nucleotides. The binding of the natural inhibitor, UDP-xylose, will be examined in similar fashion. Further insight into the reaction mechanism will be sought by studying the various isotope exchange reactions which the enzyme can undergo, and the effect of various inhibitors on these exchange reactions, as compared to the forward reaction. In addition, attempts will be made to isolate a fragment of the hypothetical enzyme-substrate intermediate, which indirect evidence suggests to be a thioester.