In enzymology, a ribosylpyrimidine nucleosidase () is an enzyme that catalyzes the chemical reaction a pyrimidine nucleoside + H2O D-ribose + a pyrimidine base Thus, the two substrates of this enzyme are pyrimidine nucleoside and H2O, whereas its two products are D-ribose and pyrimidine base. This enzyme belongs to the family of hydrolases, specifically those glycosylases that hydrolyse N-glycosyl compounds. The systematic name of this enzyme class is pyrimidine-nucleoside ribohydrolase. Other names in common use include N-ribosylpyrimidine nucleosidase, pyrimidine nucleosidase, N-ribosylpyrimidine ribohydrolase, pyrimidine nucleoside hydrolase, RihB, YeiK, and nucleoside ribohydrolase. This enzyme participates in purine metabolism and pyrimidine metabolism. Structural studies As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and . References EC 3.2.2 Enzymes of known structure