The function of UCK1 (uridine-cytidine kinase 1, Ensembl gene identifier ENSG00000130717) is as follows. Phosphorylates uridine and cytidine to uridine monophosphate and cytidine monophosphate (PubMed:11306702). Does not phosphorylate deoxyribonucleosides or purine ribonucleosides (PubMed:11306702). Can use ATP or GTP as a phosphate donor (PubMed:11306702). Can also phosphorylate cytidine and uridine nucleoside analogs such as 6- azauridine, 5-fluorouridine, 4-thiouridine, 5-bromouridine, N(4)- acetylcytidine, N(4)-benzoylcytidine, 5-fluorocytidine, 2-thiocytidine, 5-methylcytidine, and N(4)-anisoylcytidine (PubMed:11306702). .