Peroxidase from peach fruit: thermal Stability

摘要

Peroxidase from peach fruit was purified 28.9-fold by DEAE-cellulose, Sephadex G-100 and hydroxylapatite chromatography. The purified enzyme showed only one peak of activity with an optimum pH of 5.0 and temperature of 40oC. The calculated activation energy (Ea) for the reaction was 7.97 kcal/mol. The enzyme was heat-labile in the temperature range of 60 to 80oC with a fast inactivation at 80oC. PAGE of the inactivation course at 70oC showed only one band of activity. Different sugars increased the heat stability of the activity in the following order: sucrose>lactose>glucose>fructose. Measurement of residual activity showed a stabilizing effect of sucrose at various temperature/sugar concentrations (10 to 40%, w/w) with the Ea for inactivation increasing with sucrose concentration from 0 to 20% (w/w). After inactivation at 70oC and 75oC the enzyme was able to be reactivated by up to 40% of the initial activity when stored at 30oC.