Uridine Diphosphoglucose, Uridine Diphosphogalactose, Uridine Triphosphate and Uridine Diphosphoglucuronic Acid

Abstract

This chapter describes the enzymatic determination of uridine diphosphoglucose (UDPG), uridine diphosphogalactose (UDPGal), uridine triphosphate (UTP), and uridine diphosphoglucuronic acid (UDPGA). With the exception of the determination of UDPGA, all the other methods that are described in the chapter are based on the spectrophotometric measurement of the reduction of diphosphopyridine nucleotide (DPN) or triphosphopyridine nucleotide (TPN). The method for the determination of UDPG involves uridyl transferase, phosphoglucomutase, and glucose-6-phosphate dehydrogenase. Pyrophosphorolytic cleavage of UDPG yields UTP and G-l-P. The G-l-P is converted to G-6-P and the latter is oxidized to 6-PG by TPN. The method for the determination of UDPGal is based on the principle that UDPGal-4-epimerase converts UDPGal to UDPG. The UDPG is then determined by any one of the methods that is described in the chapter. There are two methods for the determination of UTP. The first method estimates all the nucleoside triphosphates present in the sample. The nucleoside diphosphokinase of Berg and Joklik is used for this method. In the second method, the UTP is converted to UDPG and the latter is determined with uridyl transferase and UDPG dehydrogenase.