Kinetic and Thermodynamic Characterization of Glucoamylase from Colletotrichum sp. KCP1

Extracellular glucoamylase of Colletotrichum sp. KCP1 produced through solid state fermentation was purified by two steps purification process comprising ammonium sulphate precipitation followed by gel permeation chromatography (GPC). The Recovery of glucoamylase after GPC was 50.40 % with 19.3-fold increase in specific activity. The molecular weight of enzyme was found to be 162.18 kDa by native-PAGE and was dimeric protein of two sub-units with molecular weight of 94.62 and 67.60 kDa as determined by SDS-PAGE. Activation energy for starch hydrolysis was 26.45 kJ mol^?1 while temperature quotient (Q₁₀) was found to be 1.9. The enzyme was found to be stable over wide pH range and thermally stable at 40–50 °C up to 120 min while exhibited maximum activity at 50 °C with pH 5.0. The pKa₁ and pKa₂ of ionisable groups of active site controlling V_max were 3.5 and 6.8, respectively. V_max, K_m and K_cat for starch hydrolysis were found to be 58.82 U ml^?1, 1.17 mg (starch) ml^?1 and 449 s^?1, respectively. Activation energy for irreversible inactivation (E_a(d)) of glucoamylase was 74.85 kJ mol^?1. Thermodynamic parameters of irreversible inactivation of glucoamylase and starch hydrolysis were also determined.