In enzymology, a purine nucleosidase () is an enzyme that catalyzes the chemical reaction a purine nucleoside + H2O D-ribose + a purine base Thus, the two substrates of this enzyme are purine nucleoside and H2O, whereas its two products are D-ribose and purine 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 purine-nucleoside ribohydrolase. Other names in common use include nucleosidase, purine beta-ribosidase, purine nucleoside hydrolase, purine ribonucleosidase, ribonucleoside hydrolase, nucleoside hydrolase, N-ribosyl purine ribohydrolase, nucleosidase g, N-D-ribosylpurine ribohydrolase, inosine-adenosine-guanosine preferring nucleoside hydrolase, purine-specific nucleoside N-ribohydrolase, IAG-nucleoside hydrolase, and IAG-NH. This enzyme participates in purine metabolism and nicotinate and nicotinamide metabolism. Structural studies As of late 2007, 11 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , , , , and . References EC 3.2.2 Enzymes of known structure