Inositol-1,3,4,5,6-Pentakisphosphate-2-Kinase (IPPK)

Inositol phosphates (InsPs) are signaling molecules with multiple roles in cells. In particular InsP6 is involved in mRNA export and editing or chromatin remodeling among other events. InsP6 accumulates as mixed salts (phytate) in storage tissues of plants and plays a key role in their physiology. Human diets that are exclusively grain-based provide an excess of InsP6 that, through chelation of metal ions, may have a detrimental effect on human health. Ins(1,3,4,5,6)P5 2-kinase (InsP5 2-kinase or Ipk1) catalyses the synthesis of InsP6 from InsP5 and ATP, and is the only enzyme that transfers a phosphate group to the axial 2-OH of the myo-inositide.  The key residues in substrate binding are identified, with Asp368 being responsible for recognition of the axial 2-OH.