Regulates the phosphatidylinositol (4,5)-diphosphate levels on the cytoplasmic surface of the endoplasmic reticulum and thereby regulates secretion. Does not utilize phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2), nor phosphatidylinositol 3-phosphate (PtdIns(3)P) and phosphatidylinositol 4-phosphate (PtdIns(4)P). 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 Present with 1200 molecules/cell in log phase SD medium. Belongs to the inositol 1,4,5-trisphosphate 5-phosphatase family.