Bifunctional inositol kinase that acts in concert with the IP6K kinases to synthesize the diphosphate group-containing inositol pyrophosphates diphosphoinositol pentakisphosphate, PP-InsP5, and bis-diphosphoinositol tetrakisphosphate, (PP)2-InsP4 (PubMed:17412958). Phosphorylates inositol hexakisphosphate (InsP6) at position 1 to produce PP-InsP5 which is in turn phosphorylated by IP6Ks to produce (PP)2-InsP4. Alternatively, phosphorylates PP-InsP5 at position 1, produced by IP6Ks from InsP6, to produce (PP)2-InsP4 (By similarity). Required for maintaining cellular integrity, normal growth and interactions with the ARP complex (PubMed:10388810). Acts as a regulator of the PHO80-PHO85 cyclin/cyclin-dependent kinase (CDK) complex, thereby regulating signaling of phosphate availability (PubMed:17412959). Required for the function of the cortical actin cytoskeleton, possibly by participating in correct F-actin localization and ensuring polarized growth (PubMed:10388810). Regulates polarized growth and modulates interphase microtubule cytoskeleton. Regulates microtubule dynamics without the requirement of microtubule plus-end tracking protein Mal3. Required for growth zone selection (By similarity). 1D-myo-inositol hexakisphosphate + ATP = 1-diphospho-myo-inositol 2,3,4,5,6-pentakisphosphate + ADP 5-diphospho-1D-myo-inositol 1,2,3,4,6-pentakisphosphate + ATP + H(+) = 1,5-bis(diphospho)-1D-myo-inositol 2,3,4,6-tetrakisphosphate + ADP The N-terminal kinase domain produces inositol polyphosphates. The C-terminal acid phosphatase-like domain binds inositol polyphosphates and negatively regulates their accumulation. The C-terminal domain reduces the amount of inositol pyrophosphates in a dose-dependent manner in vitro. Present with 8810 molecules/cell in log phase SD medium. Belongs to the histidine acid phosphatase family. VIP1 subfamily. Although related to histidine acid phosphatase proteins, it lacks the conserved active sites, suggesting that it has no phosphatase activity.