Putative uridine kinase identified in a screen for mutants with increased levels of rDNA transcription. ATP + uridine = ADP + H(+) + UMP ATP + cytidine = ADP + CMP + H(+) Pyrimidine metabolism; CTP biosynthesis via salvage pathway; CTP from cytidine: step 1/3. Pyrimidine metabolism; UMP biosynthesis via salvage pathway; UMP from uridine: step 1/1. Present with 4280 molecules/cell in log phase SD medium. Belongs to the uridine kinase family.