Change in kinetic properties and metabolic clearance of UDP-glucuronyltransferase for p-phenyl benzoic acid in developing fetus of rat.

The hepatic microsomal UDP-glucuronyltransferase (UDPGT) for p-phenyl benzoic acid (PPBA) in the developing fetus of rat was investigated. The kinetic properties of UDPGT in microsome of fetus changed during developmental period. The value of the Vmax for PPBA and uridine 5'-phosphoglucuronic acid (UDPGA) per mg protein increased with the day of gestation, remarkably between the 19th and 21st day of gestation. The developmental profile of the Vmax per g liver was similar to the Vmax per mg protein. Whereas the Vmax in whole liver showed rapid increase during development comparing with the Vmax per g liver. The Km for PPBA and UDPGA showed slower increase with the day of gestation than the corresponding Vmax.