MYOINOSITOL POLYPHOSPHATE INTERMEDIATES IN THE DEPHOSPHORYLATION OF PHYTIC ACID BY ACID-PHOSPHATASE WITH PHYTASE ACTIVITY FROM RICE BRAN

Myo-inositol phosphate intermediates formed during dephosphorylation of phytic acid (by rice bran acid phosphatase with phytase activity F2) were isolated by ion-exchange chromatography. Hydrolysis of phytic acid proceeded via L-myo-inositol 1,2,3,4,5 and d-myo-inositol 1,2,4,5,6-pentakisphosphate, d-myo-inositol 1,2,5,6 and l-myo-inositol 1,2,3,4-tetrakisphosphate, d-myo-inositol 1,2,6 and myo-inositol 1,2,3-trisphosphate, d-myo-inositol 1,2-bisphosphate and finally myo-inositol monophosphate (myo-inositol 2, 93%; d-myo-inositol 1, 7%). Six percent of myo-inositol and 85% of Pi were found in the reaction mixture when the hydrolysis of phytic acid by the enzyme did not proceed further. The initial points of dephosphorylation of phytic acid by the phytase took place at l-myo-inositol 6 (85%), d-myo-inositol 3 (7%), myo-inositol 2 (5%), and myo-inositol 5 (3%) at the positions of the myo-inositol ring. © 1990 by the Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.