Kinetics and thermodynamics of heat inactivation of sorghum peroxidase

Crude peroxidase was extracted from sorghum seeds four days after germination. It was purified 86.30-fold by DEAE-Cellulose ion exchange chromatography. The kinetics of thermal inactivation was first order in the temperature range of 50 degrees-80 degrees C. At 80 degrees C, the activation energy (Delta Ea) for inactivation determined from the Arhrenius plot was -2.983 kcal/mole. The free energy change (Delta G) was 64,416.69 kcal/mol; enthalpy (Delta H) and entropy (Delta S) changes for inactivation were -2,937.83 kcal/mol and -190.81 kcal/mol, respectively. Regeneration of activity after inactivation was observed, with the regenerated enzyme molecule being less stable than the native enzyme.