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Purification and Biochemical Characterization of Acid Phosphatase from Vigna aconitifolia

Author(s): Mohammed A. Al-Omair

Journal: American Journal of Plant Physiology
ISSN 1557-4539

Volume: 5;
Issue: 6;
Start page: 361;
Date: 2010;
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Keywords: optimum temperature | optimum pH | Specific activity | active sites and enzyme kinetics

In present study, isolation and purification of Acid Phosphatase (AP) from the shoot of Vigna aconitifolia were conducted. The purification processes included the enzyme precipitation by ammonium sulphate and chromatographic adsorption by DEAE-cellulose and sephadex G200. This study showed a purification of AP up to 60 folds with specific activity of 280 U mg-1 protein. The optimal pH value was found to be 5.4. By studying the relationship between log V and pH, it was found that two amino acid residues namely cysteine and histidine are involved in the catalytic activity of AP. This indicate that Vigna aconitifolia AP is an –SH group dependent enzyme. The highest enzyme activity was recorded after 30 min of incubation in the reaction mixture. The optimal temperature for AP activity was 30°C. The activation energy was 0.44 kJ mol-1. After 50°C the Vigna aconitifolia AP activity was decreased continuously by prolongation of incubation period. When fructose-6-phosphate and sodium phytate were used instead of p-nitrophenyl phosphate (p-NPP), they expressed 44.3 and 67.1%, respectively of the enzyme activity with p-NPP as substrate. Km value for p-NPP was 133 mM and Vmax 27.8 nmol min-1.
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