Inositol polyphosphate 1-phosphatase?is an?enzyme?that, in humans, is encoded by the?INPP1?gene. INPP1 encodes the enzyme inositol polyphosphate-1-phosphatase, one of the enzymes involved in phosphatidylinositol signaling pathways. This enzyme removes the phosphate group at position 1 of the inositol ring from the polyphosphates inositol 1,4-bisphosphate and inositol 1,3,4-trisphophosphate.