In enzymology, an adenosine-tetraphosphatase (EC 3.6.1.14) is an enzyme that catalyzes the chemical reaction

adenosine 5'-tetraphosphate + H₂O ${\displaystyle \rightleftharpoons }$ ATP + phosphate

Thus, the two substrates of this enzyme are adenosine 5'-tetraphosphate and H₂O, whereas its two products are ATP and phosphate.

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 adenosine-tetraphosphate phosphohydrolase. This enzyme participates in purine metabolism.

As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code 2V7Q.