In enzymology, a pterin deaminase () is an enzyme that catalyzes the chemical reaction 2-amino-4-hydroxypteridine + H2O 2,4-dihydroxypteridine + NH3 Thus, the two substrates of this enzyme are 2-amino-4-hydroxypteridine and H2O, whereas its two products are 2,4-dihydroxypteridine 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-amino-4-hydroxypteridine aminohydrolase. This enzyme is also called acrasinase. References EC 3.5.4 Enzymes of unknown structure