Catalyzes the reversible phosphorylytic cleavage of uridine and deoxyuridine to uracil and ribose- or deoxyribose-1-phosphate (PubMed:7488099). The produced molecules are then utilized as carbon and energy sources or in the rescue of pyrimidine bases for nucleotide synthesis. phosphate + uridine = alpha-D-ribose 1-phosphate + uracil Pyrimidine metabolism; UMP biosynthesis via salvage pathway; uracil from uridine (phosphorylase route): step 1/1. Homodimer. By vitamin D3 and a mixture of inflammatory cytokines: TNF, IL1/interleukin-1 and IFNG/IFN-gamma. Inactive. Belongs to the PNP/UDP phosphorylase family.