Catalyzes the reversible phosphorylytic cleavage of uridine and deoxyuridine to uracil and ribose- or deoxyribose-1-phosphate (PubMed:12849978, PubMed:21855639). The produced molecules are then utilized as carbon and energy sources or in the rescue of pyrimidine bases for nucleotide synthesis (Probable). Shows broad substrate specificity and accepts uridine, deoxyuridine, and thymidine as well as the two pyrimidine nucleoside analogs 5-fluorouridine and 5-fluoro-2(')-deoxyuridine as substrates (PubMed:12849978). phosphate + uridine = alpha-D-ribose 1-phosphate + uracil A conditional disulfide bridge can form within the protein that dislocates a critical phosphate-coordinating arginine Arg-100 away from the active site, disabling the enzyme. Pyrimidine metabolism; UMP biosynthesis via salvage pathway; uracil from uridine (phosphorylase route): step 1/1. Homodimer. Predominantly expressed in kidney. Belongs to the PNP/UDP phosphorylase family. Truncated N-terminus.