Structural Impact of Chelation on Phytate, a Highly Phosphorylated Biomolecule

An important biomolecule found in plant seeds and tissues, and in eukaryotic cells is myo‐inositol‐1,2,3,4,5,6‐hexakisphosphate (phytate, IP6). Phytate has many roles, including phosphate, myo‐inositol, and mineral storage and retrieval in plants, and a number of metabolic roles, not all of which are known. Despite the importance of phytate in biology, structural information is limited. Aside from this report of the potassium phytate structure, K3[H9IP6]·2H2O, only the structures of the sodium and zinc salts have appeared. The potassium structure reveals the importance of metal ion chelation in stabilizing the conformation, and the two previously reported structures support this finding. Potassium ion and hydrogen bond bridges link the interwoven phytate networks throughout the lattice. 1H NMR (800 MHz) titrations show the conformation crossover from the 1a5e to the 5a1e conformation between pH 9 and 10, and detailed 1H deconvolution studies at low pH reveal the underlying pattern assignments for individual protons. The crystal structure of the potassium salt of phosphorylated myo‐inositol (phytate), a multi‐tasking biological anion, provides insight to the structural influence of metal ion chelation. Potassium ions and hydrogen bond bridges also serve to interlink phytate ions throughout the crystal lattice. High field proton NMR studies provide solution snapshots of conformation changes as a function of pH.