In enzymology, a diaminohydroxyphosphoribosylaminopyrimidine deaminase () is an enzyme that catalyzes the chemical reaction 2,5-diamino-6-hydroxy-4-(5-phosphoribosylamino)pyrimidine + H2O 5-amino-6-(5-phosphoribosylamino)uracil + NH3 Thus, the two substrates of this enzyme are 2,5-diamino-6-hydroxy-4-(5-phosphoribosylamino)pyrimidine and H2O, whereas its two products are 5-amino-6-(5-phosphoribosylamino)uracil and NH3. This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds (specifically in cyclic amidines). The systematic name of this enzyme class is 2,5-diamino-6-hydroxy-4-(5-phosphoribosylamino)pyrimidine 2-aminohydrolase. This enzyme participates in riboflavin metabolism. Structural studies As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes , , , , , and . References EC 3.5.4 Enzymes of known structure