Biochemical and Thermodynamic Characterization of β amylase from Dioscorea alata L.

Abstract

β-amylase (E.C.3.2.1.2) is a starch hydrolyzing enzyme fondly used in foods, pharmaceuticals, and brewing industries to convert starch into maltose. The aim of this study was to determine the physicochemical, kinetic, and thermodynamic properties, as well as the potential industrial use of β-amylase from Dioscorea alata L. Studying the enzyme stability with Arrhenius methods, showed that the enzyme was stable at a temperature range of 20–500C, and had good pH stability by retaining over 50 % of its initial activity over a wide range of pH from 4 – 8 and kinetic stability by increasing the half-life of the enzyme. The activation energy (Ea) for catalysis by water yam β-amylase at 250C was 6.45kcal/mol. The activation energy (Ea), half-life, free energy change (ΔG‡), enthalpy change (ΔH‡), and entropy change (ΔS‡) for inactivation at optimum temperature (400C) and pH 5 were 13.92 kcal/mol, 41.25 min, 20.89 kcal/mol, 13.30 kcal/mol and -24.25 cal/mol/K respectively. Km and Vmax values were reduced from 2.25 to 2.13mg/ml and 2.95 to 1.48 µmol/min/ml respectively. The optimum pH shifted from 5 to 6, while the Optimum temperature increased from 40 to 500C after immobilization. Enzyme retained up to 67 % activity after 5 cycles. The enzyme would be of importance in manufacturing companies based on the kinetics and application features reported in this study since it is a cheap and readily available source.