Pyrimidine-nucleoside phosphorylase

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


 * a pyrimidine nucleoside + phosphate $$\rightleftharpoons$$ 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
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and.