Partial purification and characterization of L-myo-Inositol-1-phosphate synthase of pteridophytic origin Dhani Raj Chhetri 1* , Asok Kumar Mukherjee 2 , Jukta Adhikari 3 1 Plant Physiology and Biochemistry Laboratory, Post Graduate Department of Botany, Darjeeling Government College, Darjeeling-734 101, WB, India 2 Biochemistry and Molecular Biology Laboratory, Department of Botany, University of Burdwan, Golapbag, Burdwan-713 104, WB, India 3 Biochemistry Laboratory, Department of Botany, Presidency College, College Street, Kolkata, WB, India * for correspondence: Post Box No. 79, Darjeeling-H. P. O., 734101, WB, India, e-mail: munal@sancharnet.in Key words: D-glucose-6-phosphate, Diplopterygium glaucum, enzyme purification, myo-Inositol, Pterido- phytes Abstract 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. avail- able in Darjeeling Himalayas. The enzyme was partially puri- fied 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-phosphte 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 Cd 2+ and highly inhibited by Li + and Hg 2+ . 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 rnax 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. List of abbreviations: MIPS=L-myo-inositol-1-phos- phate synthase, G-6-P=Glucose-6-phosphate, ME= 2-mercaptoethanol, I-1-P=Inositol-1-phosphate Introduction Myo-Inositol is an essential nutrient for growth and development of all living organism, it helps in the formation of sex units and acts as an integral part of storage phosphates in seeds (Murashige and Skoog 1962, Maiti and Loewus 1978, Chiu et al. 2003). It also forms cell wall polysaccharides and essential component of myelin in the central nervous system (Adhikari and Majumder, 1988). The biosynthesis of myo-Inositol from Glucose-6-phosphate was documented from a number of biological systems (Loewus and Loewus 1983). D-glucose-6-phos- phate (G-6-P) irreversibly isomerizes to L-myo -inositol-1-phosphate by L-myo-inositol-1-phos- phate synthase (MIPS). The product of this enzyme generates free myo-inositol on dephosphorylation (Loewus and Loewus 1973). The enzyme, MIPS was isolated and characterized from a number of 101 ACTA PHYSIOLOGIAE PLANTARUM Vol. 28. No. 2. 2006: 101-107