myo-inositol phosphate isomers generated by the action of a phytase from a malaysian waste-water bacterium

Using a combination of High-Performance Ion Chromatography analysis and kinetic studies, the pathway of myo-inositol hexakisphosphate dephosphorylation by a phytase from a Malaysian waste-water bacterium was established. The data demonstrate that the phytase preferably dephosphorylates myo-inositol hexakisphosphate in a stereospecific way by sequential removal of phosphate groups via D-I(1,2,3,4,5)P-5, D-I(2,3,4,5)P-4, D-I(2,3,4)P-3, D-I(2,3)P-2 to finally I(2)P. It was estimated that more than 90% of phytate hydrolysis occurs via D-I(1,2,3,4,5)P-5. Thus, the phytase from the Malaysian waste-water bacterium has to be considered a 6-phytase (E.C. 3.1.3.26). A second pathway of minor importance could be proposed which is in accordance with the results obtained from analysis of the dephosphorylation products formed by the action of the phytase under investigation on myo-inositol hexakisphosphate. It proceeds via D/L-I(1,2,4,5,6)P-5, D/L-I(1,2,4,5)P-4, D/L-I(1,2,4)P-3, D/L-I(2,4)P-2 to finally I(2)P.