The protein encoded by this gene catalyzes the phosphorylation of phosphatidylinositol-5-phosphate on the fourth hydroxyl of the myo-inositol ring to form phosphatidylinositol-5,4-bisphosphate. This gene is a member of the phosphatidylinositol-5-phosphate 4-kinase family. The encoded protein sequence does not show similarity to other kinases, but the protein does exhibit kinase activity. Additionally, the encoded protein interacts with p55 TNF receptor. [provided by RefSeq, Jul 2008].