In enzymology, an aminoimidazolase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are 4-aminoimidazole and H<sub>2</sub>O, whereas its two products are unidentified product and NH<sub>3</sub>.
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 4-aminoimidazole aminohydrolase. This enzyme is also called 4-aminoimidazole hydrolase. This enzyme participates in purine metabolism. It employs one cofactor, iron.