Phosphatidylinositol-4,5-bisphosphate 4-phosphatase (EC 3.1.3.78, phosphatidylinositol-4,5-bisphosphate 4-phosphatase I, phosphatidylinositol-4,5-bisphosphate 4-phosphatase II, type I PtdIns-4,5-P<sub>2</sub> 4-Ptase, type II PtdIns-4,5-P<sub>2</sub> 4-Ptase, IpgD, PtdIns-4,5-P<sub>2</sub> 4-phosphatase type I, PtdIns-4,5-P<sub>2</sub> 4-phosphatase type II, type I phosphatidylinositol-4,5-bisphosphate 4-phosphatase, type 1 4-phosphatase) is an enzyme with systematic name 1-phosphatidyl-1<small>D</small>-myo-inositol-4,5-bisphosphate 4-phosphohydrolase. This enzyme catalyses the following chemical reaction
This enzyme participates in one of the mammalian pathways for degradation of 1-phosphatidyl-1<small>D</small>-myo-inositol 4,5-bisphosphate [PtdIns(4,5)P<sub>2</sub>].