In enzymology, 1-phosphatidylinositol-4-phosphate 5-kinase (EC 2.7.1.68) is an enzyme that catalyzes the chemical reaction

ATP + 1-phosphatidyl-1D-myo-inositol 4-phosphate ${\displaystyle \rightleftharpoons }$ ADP + 1-phosphatidyl-1D-myo-inositol 4,5-bisphosphate

Thus, the two substrates of this enzyme are ATP and 1-phosphatidyl-1D-myo-inositol 4-phosphate, whereas its two products are ADP and 1-phosphatidyl-1D-myo-inositol 4,5-bisphosphate.

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with an alcohol group as acceptor. The systematic name of this enzyme class is ATP:1-phosphatidyl-1D-myo-inositol-4-phosphate 5-phosphotransferase. Other names in common use include diphosphoinositide kinase, PIP kinase, phosphatidylinositol 4-phosphate kinase, phosphatidylinositol-4-phosphate 5-kinase, and type I PIP kinase. This enzyme participates in 3 metabolic pathways: inositol phosphate metabolism, phosphatidylinositol signaling system, and regulation of the actin cytoskeleton.

As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 1BO1 and 2GK9.

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• Kai M, Salway JG, Michell RH, Hawthorne JN (1966). "The biosynthesis of triphosphoinositide by rat brain in vitro". Biochem. Biophys. Res. Commun. 22 (4): 370–375. doi:10.1016/0006-291X(66)90655-3.
• Rameh LE, Tolias KF, Duckworth BC, Cantley LC (1997). "A new pathway for synthesis of phosphatidylinositol-4,5-bisphosphate". Nature. 390 (6656): 192–6. Bibcode:1997Natur.390..192R. doi:10.1038/36621. PMID 9367159. S2CID 4403301.