UMP-CMP kinase catalyses an important step in the phosphorylationofUTP, CTPanddCTP. It is also involved in the necessary phosphorylation by cellular kinases of nucleoside analogs used in antiviral therapies. The reactivity of human UMP-CMP kinase towards natural substrates and nucleotide analogs was reexamined. The expression of the recombinant enzyme and conditions for stability of the enzyme were improved. Substrate inhibition was observed for UMP and CMP at concentrations higher than mM, but not for dCMP. The antiviral analogL-3TCMP was found to be an efficient substrate phosphorylated into L-3TCDP by human UMP-CMP kinase. .
