diphosphate + H2O = H(+) + 2 phosphate Binds tightly a transition metal ion; prefers Co(2+) over Mn(2+). Mg(2+) ions are required for optimal catalytic activity. Inhibited by AMP and ADP with 25% and 35% of activity remaining, respectively, at saturating conditions. Activated 5-fold by diadenosine polyphosphates(Ap[n]A) with n>2 (Ap3A, Ap4A, Ap5A, Ap6A) at saturating conditions. Homodimer. Belongs to the PPase family.