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.