The thermal stability of purified acid phosphatase from the germinating seedlings of Coronopus didymus (Jangli halon) was investigated by studying the impact of various thermodynamic parameters [t1/2, Ed, ΔH° (enthalpy change), ΔG° (free energy change), and ΔS° (entropy change)] of heat treatment in the temperature range of 55-75 °C. The thermal denaturation of acid phosphatase, assessed by loss in activity, was evidently followed by first-order kinetics, which varies with time and yield during the process of denaturation. The half-life of the enzyme was 693 min at 55 °C. The Ed (activation energy of denaturation) was calculated by the Arrhenius plot (30 kcal mol-1), and the Z-value was 17.3 °C. The various thermodynamic parameters studied were as follows: ΔH°, the change in enthalpy of inactivation, was 121.93 kJ mol-1 at 55 °C; ΔG°, the change in free energy of inactivation, was 110.65 kJ mol-1 at 55 °C; and ΔS°, the change in entropy of inactivation, was 34.39 J mol-1 k-1 at 55 °C. This suggests that acid phosphatase activity is thermostable to long heat treatment up to 60 °C.
Keywords: Coronopus didymus; acid phosphatase; biocatalyst; inactivation; thermodynamic; thermostability.