In enzymology, an uridine phosphorylase (EC 2.4.2.3) is an enzyme that catalyzes the chemical reaction

uridine + phosphate ${\displaystyle \rightleftharpoons }$ uracil + alpha-D-ribose 1-phosphate

This article's use of external links may not follow Wikipedia's policies or guidelines. (February 2022)

Thus, the two substrates of this enzyme are uridine and phosphate, whereas its two products are uracil and alpha-D-ribose 1-phosphate.

This enzyme belongs to the family of glycosyltransferases, specifically the pentosyltransferases. The systematic name of this enzyme class is uridine:phosphate alpha-D-ribosyltransferase. Other names in common use include pyrimidine phosphorylase, UrdPase, UPH, and UPase. This enzyme participates in pyrimidine metabolism.

As of late 2007, 27 structures have been solved for this class of enzymes, with PDB accession codes 1K3F, 1LX7, 1RXC, 1RXS, 1RXU, 1RXY, 1RYZ, 1SJ9, 1SQ6, 1T0U, 1TGV, 1TGY, 1U1C, 1U1D, 1U1E, 1U1F, 1U1G, 1Y1Q, 1Y1R, 1Y1S, 1Y1T, 1ZL2, 2HN9, 2HRD, 2HSW, 2HWU, and 2I8A.