Comparative characteristics of cytosolic and chloroplastidial D/L- myo-inositol-1-phosphate phosphatase partially purified from Enteromorpha intestinalis (L.) Nees (a marine macro alga) grown under high salinity niche

The present investigation describes a protocol for partial purification and basic characterization of one of the key enzymes of myo-inositol biosynthesis, D/L- myo- Inositol-1-phosphate phosphatase (MIPP), from a marine macro alga (Enteromorpha intestinalis) growing under varying salinity conditions of Chilika lagoon (Odisha, India). Cytosolic and chloroplastidial forms of MIPP were partially purified to about 55- and 16- folds respectively following lowspeed centrifugation, high-speed centrifugation, 0-80% ammonium sulfate precipitation, successive chromatography through CM-cellulose, Sephadex G-200 and UltrogelAcA 34 columns. The apparent molecular weights of the native cytosolic and plastidial forms of MIPP were determined to be 146 and 148 kDa respectively. Cytosolic and plastidial MIPP were remarkably active within the temperature range of 20-40°C and function within a narrow pH range (7.0-7.5). Using nonlinear regression kinetics, the Km value for D-MIP of the cytosolic MIPP and its plastidial iso-form were 0.07277 mM and 0.07332 mM respectively. Different monovalent as well as divalent cations exhibited variable effects on enzyme activity of either preparation. The activity of MIPP was remarkably found to increase proportionately with the salinity of Chilika lagoon.