ATP diphosphatase  In enzymology, an ATP diphosphatase () is an enzyme that catalyzes the chemical reaction  Thus, the two substrates of this enzyme are ATP and H2O, whereas its two products are AMP and diphosphate. This enzyme belongs to the family of hydrolases, specifically those acting on acid anhydrides in phosphorus-containing anhydrides. The systematic name of this enzyme class is ATP diphosphohydrolase (diphosphate-forming). Other names in common use include ATPase, ATP pyrophosphatase, adenosine triphosphate pyrophosphatase, and ATP diphosphohydrolase [ambiguous]. This enzyme participates in purine metabolism and pyrimidine metabolism.