Partial purification and characterization of L-myo-inositol-1-phosphate synthase of pteridophytic origin

Myo-Inositol is an important metabolite for normal growth and development of all living organisms. The cellular level of myo-inositol is controlled by the enzyme L-myo- inositol-1-phosphate synthase (MIPS) EC 5.5.1.4]. Appreciable level of MIPS activity was detected from the common pteridophytes like Dicranopteris, Diplazium, Diplopterygium, Equisetum, Lycopodium, Polypodium, Pteridium, Selaginella etc. available in Darjeeling Himalayas. The enzyme was partially purified from the reproductive pinnules of Diplopterygium glaucum (Thunb.) Nakai. The purification obtained was about 81 fold and the recovery was about 13.5 %. The final enzyme preparation specifically utilized D-Glucose-6-phosphate and NAD+ as its substrate and co-factor respectively. It shows pH optima between 7.0 and 7.5 while the temperature maximum was at 35 °C. The enzyme activity was slightly inhibited by Na⁺ and Cd²⁺ and highly inhibited by Li⁺ and Hg²⁺. The K _rn values for D-glucose-6-phosphate and NAD+ was found to be as 0.83 mM and 0.44 mM respectively while the V _max values were 1.42 mM and 1.8 mM for D-glucose-6-phosphate and NAD+ respectively. The present study indicates the universal occurrence of this enzyme in all plant groups.