In enzymology, an ATP deaminase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are ATP and H<sub>2</sub>O, whereas its two products are ITP 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 ATP aminohydrolase. This enzyme is also called adenosine triphosphate deaminase.