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. 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 (By similarity). 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 (PubMed:25254656). 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. Hypersensitive to microtubule poison thiabendazole (TBZ). Significantly increased number of interphase microtubules that depolymerize at the lateral cortex/cytoplasm and not at the cell tip. Microtubules touch the lateral cortex and become depolymerized instead of being deflected as do the microtubules of wild-type. 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.