In enzymology, a bis(5'-nucleosyl)-tetraphosphatase (symmetrical) () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are P1,P4-bis(5'-adenosyl) tetraphosphate and H<sub>2</sub>O, whereas its product is ADP.
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 P1,P4-bis(5'-nucleosyl)-tetraphosphate nucleosidebisphosphohydrolase. Other names in common use include diadenosinetetraphosphatase (symmetrical), dinucleosidetetraphosphatasee (symmetrical), symmetrical diadenosine tetraphosphate hydrolase, adenosine tetraphosphate phosphodiesterase, Ap4A hydrolase, bis(5'-adenosyl) tetraphosphatase, diadenosine tetraphosphate hydrolase, diadenosine polyphosphate hydrolase, diadenosine 5',5-P1,P4-tetraphosphatase, diadenosinetetraphosphatase (symmetrical), 1-P,4-P-bis(5'-nucleosyl)-tetraphosphate, and nucleosidebisphosphohydrolase. This enzyme participates in purine metabolism.
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and .