Phosphatidylinositol phosphate kinase (PIPK) catalytic domain found in phosphatidylinositol 4-phosphate 5-kinase type-1 alpha (PIP5K1alpha) and similar proteins
PIP5K1alpha (EC 2.7.1.68), also termed PIP5K1A, or PtdIns(4)P-5-kinase 1 alpha, or 68 kDa type I phosphatidylinositol 4-phosphate 5-kinase alpha, or PIPKI-alpha, catalyzes the phosphorylation of phosphatidylinositol 4-phosphate (PtdIns4P) to form phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). It mediates extracellular calcium-induced keratinocyte differentiation. Unlike other type I phosphatidylinositol-4-phosphate 5-kinase (PIPKI) isoforms, PIP5K1alpha regulates directed cell migration by modulating Rac1 plasma membrane targeting and activation. This function is independent of its catalytic activity, and requires physical interaction of PIP5K1alpha with the Rac1 polybasic domain. The family also includes testis-specific PIP5K1A and PSMD4-like protein, also known as PIP5K1A-PSMD4 or PIPSL. It has negligeable PIP5 kinase activity and binds to ubiquitinated proteins.