Controls the cellular levels and subcellular distribution of phosphatidylinositol 3-phosphate and phosphatidylinositol 4,5-bisphosphate. Involved in distinct membrane trafficking and signal transduction pathways. Highly active against a range of soluble and lipid inositol phosphates. Active in dephosphorylating the 5-position of Ins(1,4,5)P3 and Ins(1,3,4,5)P4 and to a lesser extent Ins(1,4,5,6)P4 (By similarity). a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-4,5-bisphosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol 4-phosphate) + phosphate By stress. Belongs to the synaptojanin family. In the central section; belongs to the inositol 1,4,5-trisphosphate 5-phosphatase family.