Phosphatidylinositol 4-phosphate 5-kinase type-1 beta is a protein in humans that is encoded by PIP5K1B gene. Participates in the biosynthesis of phosphatidylinositol 4,5-bisphosphate. Mediates RAC1-dependent reorganization of actin filaments. Contributes to the activation of PLD2. Together with PIP5K1A is required after stimulation of G-protein coupled receptors for stable platelet adhesion (By similarity).