In enzymology, a 1-phosphatidylinositol-5-phosphate 4-kinase (EC 2.7.1.149) is an enzyme that catalyzes the chemical reaction ATP + 1-phosphatidyl-1D-myo-inositol 5-phosphate ADP + 1-phosphatidyl-1D-myo-inositol 4,5-bisphosphate Thus, the two substrates of this enzyme are ATP and , whereas its two products are ADP and .