Summary
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.
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A preliminary report of these results has been presented (Proc. Amer. Assoc. Cancer Res.17 : 78, 1976).
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Liacouras, A.S., Anderson, E.P. Uridine-cytidine kinase III. Competition between uridine and cytidine for a single enzyme. Mol Cell Biochem 17, 141–146 (1977). https://doi.org/10.1007/BF01730833
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DOI: https://doi.org/10.1007/BF01730833