Studies on the biosynthesis of cyclitols, XXXVI. Purification of myo-inositol-1-phosphate synthase of the duckweed, Lemna gibba, to homogeneity by affinity chromatography on NAD-Sepharose molecular and catalytic properties of the enzyme.

Using the technique of affinity chromatography on NAD-Sepharose the myo-inositol-1-phosphate synthase of Lemna gibba was purified to homogeneity. The molecular and catalytic properties of this enzyme differ very much from those of myo-inositol-1-phosphate synthase from animal sources. Thus the specific activity of the duckweed enzyme is more than two orders of magnitude higher than that of the enzyme from rat testes. It is inhibitied by EDTA and can be reactivated by Mn2. Its molecular weight (135000 +/- 5000), its subunit composition (3 subunits with identical electrophoretic behaviour) and its isoelectric point (pH 7.7) are also very different from the corresponding parameters for the animal enzyme.