METABOLISM OF INOSITOL PHOSPHATES .11. FURTHER CHARACTERIZATION OF PHYTASE FROM PHASEOLUS-AUREUS

Phytase purified to homogeneity from germinated mungbean cotyledons was inhibited by EDTA although it did not show any absolute requirement for divalent cations. Sodium fluoride, sodium citrate, mercaptoethanol and pCMB also inhibit the phytase activity but l-phenylalanine has no effect on activity. The phytase has a low affinity for inositol monophosphate. The relative rate of dephosphorylation of myo-inositol-1 -phosphate and myo-inositol-5 phosphate by phytase is 6 and 18% respectively of that of myo-inositol-hexaphosphate. Mungbean phytase cannot cleave myo-inositol-2-phosphate, 1,2-cyclic inositol phosphate, Na-β-glycerophosphate or p-nitrophenylphosphate. The relative rates of hydrolysis of different isomers of inositol hexaphosphate are in the following order: myo-IP6, > neo-IP6 > scyllo-IP6 = d-chiro-IP6, > l-chiro-IP6. This enzyme seems to be most active with myo-inositol hexaphosphate. © 1979.