Phosphatase that specifically hydrolyzes the 5-phosphate of inositol 1,4,5-trisphosphate to inositol 1,4-bisphosphate, and inositol 1,3,4,5-tetrasphosphate to inositol 1,3,4-trisphosphate (PubMed:8198557). Plays a crucial role in the survival of cerebellar Purkinje cells (By similarity). 1D-myo-inositol 1,4,5-trisphosphate + H2O = 1D-myo-inositol 1,4-bisphosphate + phosphate 1D-myo-inositol 1,3,4,5-tetrakisphosphate + H2O = 1D-myo-inositol 1,3,4-trisphosphate + phosphate Inhibited by EDTA and 2,3-bisphosphoglycerate. Interacts with TASOR. Isoprenylation at Cys-409 is required for localization at the membrane. Belongs to the inositol 1,4,5-trisphosphate 5-phosphatase type I family.