Background：Cleaves a beta-phosphate from the diphosphate groups in PP-InsP5(diphosphoinositol pentakisphosphate) and [PP]2-InsP4(bisdiphosphoinositol tetrakisphosphate), suggesting that it may play a role in signal transduction. InsP6(inositol hexakisphophate) is not a substrate. Acts as a negative regulator of the ERK1/2 pathway. Also able to catalyze the hydrolysis of dinucleoside oligophosphates, with Ap6A and Ap5A being the preferred substrates. The major reaction products are ADP and p4a from Ap6A and ADP and ATP from Ap5A. Also able to hydrolyze 5-phosphoribose 1-diphosphate.
