Uridine-cytidine kinase. III. Competition between uridine and cytidine for a single enzyme.
The combined phosphorylation of uridine and cytidine by a partially purified preparation of uridine-cytidine kinase has been studied with dual-substrate kinetics. The kinetic patterns obtained are consistent with the theoretical analysis for two competing, alternate substrates interacting with a single enzyme. Thus, despite feedback regulation of the kinase by both UTP and CTP, the results allow a clear conclusion that both nucleosides are phosphorylated by the same enzyme, and probably at a single site, rather than by two closely related isozymes, each specific for one pyrimidine.
D000494:Allosteric Regulation; D000818:Animals; D001667:Binding, Competitive; D003562:Cytidine / Q000378:metabolism*; D003570:Cytidine Triphosphate / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D010770:Phosphotransferases / Q000378:metabolism*; D014529:Uridine / Q000378:metabolism*; D014541:Uridine Kinase / Q000378:metabolism*; D014544:Uridine Triphosphate / Q000494:pharmacology
D007527:Isoenzymes; D003562:Cytidine; D003570:Cytidine Triphosphate; D010770:Phosphotransferases; D014541:Uridine Kinase; D014544:Uridine Triphosphate; D014529:Uridine