Catalysis of the reaction: 1-phosphatidyl-1D-myo-inositol 4,5-bisphosphate + H2O = 1,2-diacylglycerol + 1D-myo-inositol 1,4,5-trisphosphate + H+.
1-phosphatidyl-D-myo-inositol-4,5-bisphosphate inositoltrisphosphohydrolase activity