Analysis of the kinetic patterns of horseradish peroxidase thermal inactivation in sodium phosphate buffer solutions of different ionic strength
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The thermal inactivation of horseradish peroxidase was studied in sodium phosphate buffer solutions and in pure water at pH 7 in the temperature range of 70–95°C. The sodium phosphate ions concentration affected both the thermostability and the kinetic patterns and had a stabilizing effect. The gradual change observed at low concentrations made a series-type mechanism theoretically more coherent with the experimental observations than the conventionally applied two-fraction model. In water the kinetics is apparently First order at high temperatures, while the results obtained at 25°C support the occurrence of a series-type inactivation mechanism. The pH and enzyme concentration also affect the inactivation proFile, supporting the conclusion that the thermal inactivation is not a monomolecular process with respect to protein concentration.