Peroxidase activity in roots of arracacha affected by pH and temperature

In this paper, roots of arracacha (Arracacia xanthorrhyza Bancroft) were stored at 5oC to induce chilling injury symptoms and stress-related peroxidase activity. Later, peroxidase kinetic activity was determined in different pH and temperature conditions. For this, soluble crude extract was sequentially saturated with ammonium sulfate, obtaining a semi-purified enzyme solution used for the analysis. Activity of peroxidase induced by the chilling at 5 o C was determined from pH 2.5 to 9.0 and at temperature ranging from 10 to 80 o C. The peroxidase had higher activity when the reaction occurred between pH 5.5 and 6.0 and at temperature of 30 o C. Complete inactivation of the activity was observed in pH 2.5 after 60 minutes of pre-incubation or at 60 o C for 10 minutes or alternatively at 70 o C after 5 minutes of pre-incubation. The enzyme is more susceptible to inactivation in acid than alkaline pHs or alternatively using heat treatment.