In enzymology, a bis(5'-nucleosyl)-tetraphosphatase (asymmetrical) () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are P1,P4-bis(5'-guanosyl) tetraphosphate and H<sub>2</sub>O, whereas its two products are GTP and GMP.
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 nucleotidohydrolase. Other names in common use include bis(5'-guanosyl)-tetraphosphatase, bis(5'-adenosyl)-tetraphosphatase, diguanosinetetraphosphatase (asymmetrical), dinucleosidetetraphosphatase (asymmetrical), diadenosine P1,P4-tetraphosphatase, dinucleoside tetraphosphatase, and 1-P,4-P-bis(5'-nucleosyl)-tetraphosphate nucleotidohydrolase. This enzyme participates in purine metabolism and pyrimidine metabolism.
As of late 2007, 7 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , and .