Pyrimidine-nucleoside phosphorylase

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pyrimidine-nucleoside phosphorylase
EC no.
CAS no.9055-35-0
IntEnzIntEnz view
ExPASyNiceZyme view
MetaCycmetabolic pathway
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

In enzymology, a pyrimidine-nucleoside phosphorylase (EC is an enzyme that catalyzes the chemical reaction

a pyrimidine nucleoside + phosphate a pyrimidine base + alpha-D-ribose 1-phosphate

Thus, the two substrates of this enzyme are pyrimidine nucleoside and phosphate, whereas its two products are pyrimidine base 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 pyrimidine-nucleoside:phosphate alpha-D-ribosyltransferase. This enzyme is also called Py-NPase. This enzyme participates in pyrimidine metabolism.

Structural studies[edit]

As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 1BRW and 2DSJ.


  • Boyer, P.D., Lardy, H. and Myrback, K. (Eds.), The Enzymes, 2nd ed., vol. 5, Academic Press, New York, 1961, p. 237-255.
  • Saunders PP, Wilson BA, Saunders GF (1969). "Purification and comparative properties of a pyrimidine nucleoside phosphorylase from Bacillus stearothermophilus". J. Biol. Chem. 244 (13): 3691–7. PMID 4978445.
  • Hamamoto T, Noguchi T, Midorikawa Y (1996). "Purification and characterization of purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase from Bacillus stearothermophilus TH 6-2". Biosci. Biotechnol. Biochem. 60 (7): 1179–80. doi:10.1271/bbb.60.1179. PMID 8782414.