Specifically hydrolyzes (di)adenosine polyphosphates but not ATP or diadenosine triphosphate, generating ATP as the product. Diadenosine hexaphosphate (Ap6A) is the preferred substrate and hydrolysis yields 2 ATP. It is the only enzyme that symmetrically hydrolyzes Ap6A. It also hydrolyzes diadenosine pentaphosphate (Ap5A), diadenosine tetraphosphate (Ap4A) and adenosine tetraphosphate (p4A). H2O + P(1),P(6)-bis(5'-adenosyl) hexaphosphate = 2 ATP + 2 H(+) H2O + P(1),P(5)-bis(5'-adenosyl) pentaphosphate = ADP + ATP + 2 H(+) H2O + P(1),P(4)-bis(5'-adenosyl) tetraphosphate = AMP + ATP + 2 H(+) Also able to use Mn(2+) and Zn(2+), but the activity is less than that obtained with Mg(2+) ions. Strongly inhibited by fluoride ions. kcat is 4.1 sec(-1) with Ap6A (at 25 degrees Celsius). kcat is 1.4 sec(-1) with p4A (at 25 degrees Celsius). kcat is 0.52 sec(-1) with Ap5A (at 25 degrees Celsius). kcat is 0.27 sec(-1) with Ap4A (at 25 degrees Celsius). Optimum pH is 8. Optimum temperature is 70 degrees Celsius. Ndx1 is stable up to 95 degrees Celsius at pH 7.5. Monomer. Belongs to the Nudix hydrolase family.