AbstractEnzymatic activities involved in the transformations of uridine nucleotides by intact erythrocytes and their subfractions have been studied and the following enzymatic activities have been identified: UTPase, UDPase, UMPase and uridylate kinase.UTPase activity was present exclusively in the stromal fraction while UMPase and uridylate kinase activities were specific in the soluble fraction. UDPase was present in both the stromal and soluble fractions.This compartmentation in erythrocytes differs from that reported for the enzymes involved in adenine nucleotides transformations. Due to its sensitivity to Zn2+, uridylate kinase could be differentiated from adenylate kinase.