In enzymology, an UDP-sugar diphosphatase (EC 3.6.1.45) is an enzyme that catalyzes the chemical reaction

UDP-sugar + H₂O UMP + alpha-D-aldose 1-phosphate

Thus, the two substrates of this enzyme are UDP-sugar and H₂O, whereas its two products are UMP and alpha-D-aldose 1-phosphate.

This enzyme belongs to the family of hydrolases, specifically those acting on acid anhydrides in phosphorus-containing anhydrides. The systematic name of this enzyme class is UDP-sugar sugarphosphohydrolase. Other names in common use include nucleosidediphosphate-sugar pyrophosphatase, nucleosidediphosphate-sugar diphosphatase, UDP-sugar hydrolase, and UDP-sugar pyrophosphatase.

As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes 1HO5, 1HP1, 1HPU, 1OI8, 1OID, and 1OIE.

• Garrett AR, Johnson LA, Beacham IR (1989). "Isolation, molecular characterization and expression of the ushB gene of Salmonella typhimurium which encodes a membrane-bound UDP-sugar hydrolase". Mol. Microbiol. 3 (2): 177–86. doi:10.1111/j.1365-2958.1989.tb01806.x. PMID 2548058. S2CID 23200294.
• Glaser L, Melo A, Paul R (1987). "Uridine diphosphate sugar hydrolase. Purification of enzyme and protein inhibitor". J. Biol. Chem. 242 (8): 1944–1954. doi:10.1016/S0021-9258(18)96092-8. PMID 5337593.