Partial Characterization of α-Amylase from Germinating Little Millets (Panicum sumatrense)
Abstract
α-Amylase, a starch splitting enzyme, was purified to homogeneity from little millet (Panicum sumatrense L. Roth ex Roem. et Schult.) cotyledons excised from 3-day-old seedlings by successive chromatography on DEAE-cellulose and Sephadex G-150. Purification achieved was 10.15 fold from the crude extract with a yield of 29% giving a final specific activity of 1001U/mg protein. SDS-PAGE showed a molecular weight of 46 kDa for the enzyme. The enzyme was characterized in terms of pH optimum and stability, temperature optimum and stability, activation energy, Km and Vmax. The enzyme displayed optimum activity at pH 5.0 and 50°C with an apparent Km value of 1.6 mg for soluble starch as substrate and Vmax 1388 units/ min/mg protein. The energy of activation (Ea) for the enzyme-catalyzed reaction was 9.7 kcal./mole. Significant enhancement in the enzyme activity was observed in the presence of metal ions like Ca2+ and Ba2+ while metal ions such as Fe2+, Hg2+ and Al3+ completely inactivated the enzyme. Incubation of the enzyme with 10mM EDTA for 30 min at 45°C results in complete loss of activity.
Key words: α-Amylase, Little millet, Characterization, Panicum sumatrense
Usha B et al. Partial Characterization of α-Amylase from Germinating Little Millets (Panicum sumatrense). J Phytol 3/1 (2011) 01-08.
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