Peroxidase from peach fruit: thermal stability

RESUMO

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 40§C. 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 80§C with a fast inactivation at 80§C. PAGE of the inactivation course at 70§C showed only one band of activity. Different sugars increased the heat stability of the activity in the following order sucrose>glucose>fructose. Measurement of residual activity showed a stabilizing effect of sucrose at various temperature/sugar concentrations (10 to 40 per cent, w/w) with the Ea for inactivation with sucrose concentration from 0 to 20 per cent (w/w). After inactivation at 70§C the enzyme was able to be reactivated by up to 40 per cent of the initial activity when stored at 30§C