Kinetic modeling of enzyme inactivation:: Kinetics of heat inactivation at 90-110 °C of extracellular proteinase from Pseudomonas fluorescens 22F

The kinetics of heat inactivation at 90-110 degrees C of the extracellular proteinase from Pseudomonas fluorescens 22F was studied. The activation enthalpy Delta H double dagger and activation entropy Delta S double dagger of the inactivation reaction, when analyzed with a first-order kinetic inactivation model, were found to be 84.5 kJ mol(-1) and -83.2 J mol(-1) K-1. Because the fit was not adequate, alternative inactivation models were proposed and modeled to fit the data. The model with the fewest parameters being statistically acceptable consisted of two sequential irreversible first-order reactions and could be used for predictive modeling of the inactivation of the proteinase. A model consisting of two consecutive irreversible reactions, in which the first reaction leads to a partially inactivated enzyme molecule with a relative specific activity of approximate to 0.6, was statistically better and also appeared to be more in accordance with the mechanism of inactivation.