The pathway of dephosphorylation of myo-inositol hexakisphosphate by phytases from wheat bran of Triticum aestivum L. cv. Nourin #61

Phytases are the primary enzymes responsible for the hydrolysis of phytic acid, myo-inositol-1, 2, 3, 4, 5, 6-hexakisphosphate (InsP(6)). The pathway of hydrolysis of InsP(6) by phytase from wheat bran of Triticum aestivum L. cv. Nourin #61 is proved in this study. Structures of the intermediates were established by a variety of nuclear magnetic resonance techniques (H-1-, two-dimensional H-1-H-1 coupling-correlation spectra and two-dimensional P-31-H-1 correlation spectra), gas chromatography, and bioassay. On the basis of the structures identified, initial hydrolysis of the phosphate ester occurs at the D/L-4 position of InsP(6) to yield D/L-Ins (1, 2, 3, 5, 6) P-5. After the dephosphorylation, the pathway of dephosphorylation is divided into two routes. The main route proceeds via D/L-Ins (1, 2, 5, 6) P-4, D/L-Ins (1, 2, 6) P-3 and D/L-Ins (1, 2) P-2, while the minor route proceeds via D/L-Ins (1, 2, 3, 6) P-4, Ins (1, 2, 3) P-3 and D/L-Ins (1, 2) P-2. D/L-Ins (1, 2) P-2 is hydrolyzed at the D/L-1 or 2-position, and finally myo-inositol is produced.