Cleaves the beta-phosphate from diphosphoinositol polyphosphates such as PP-InsP5 (diphosphoinositol pentakisphosphate), PP-InsP4 (diphosphoinositol tetrakisphosphate) and [PP]2-InsP4 (bisdiphosphoinositol tetrakisphosphate), suggesting that it may play a role in signal transduction. Diadenosine polyphosphates, particularly Ap6A (P(1),P(6)-bis(5a-adenosyl) hexaphosphate) and Ap5A (P(1),P(5)-bis(5'-adenosyl) pentaphosphate) are downstream effectors of a signaling cascade that regulates cardiac KATP channels, can also be substrates, although with lower preference than the diphosphoinositol polyphosphates. Can also catalyze the hydrolysis of 5-phosphoribose 1-diphosphate, generating the glycolytic activator ribose 1,5-bisphosphate. Does not play a role in U8 snoRNA decapping activity. Binds U8 snoRNA 