Biosynthèse de l'udpglucose par les microsomes des hépatocytes de rat

Evidence is presented to show that all enzymes and all intermediary metabolites of a UDPglucose biosynthesis pathway are present in the microsomal membranes of rat liver. Glucose 6-phosphate, glucose 1-phosphate and UDPglucose are characterized by chromatography.The properties of phosphoglucomutase and UTP: D-Glucose-1-phosphate uridyltransferase are studied. The K_m values of phosphoglucomutase at pH 7.2 and 42°C were 0.26 · 10^?3 mM for glucose 1,6-diphosphate and 80 · 10^?3 mM for glucose 1-phosphate. The K_m values of UTP: D-glucose-1-phosphate uridyltransferase at pH 8.5 and 37°C were 220 · 10^?3 mM for UTP and 166 · 10^?3 mM for glucose 1-phosphate. These values are compared to the given values for enzymes from different species, and to those found for soluble enzymes. The significance of this membranous pathway is discussed.