Influence of pH, benzoic acid, glutathione, EDTA, 4-hexylresorcinol, and sodium chloride on the pressure inactivation kinetics of mushroom polyphenoloxidase

Pressure inactivation of mushroom PPO was studied for pH values ranging fro m 4 to 8, and the effect of some antibrowning agents on the pressure stabil ity of mushroom PPO at pH 6.5 was evaluated, pH reduction below 6.5 resulte d in a lowered inactivation threshold pressure and an increase of the absol ute value of the activation volume (or a decrease of the z(p) value), the l atter two parameters reflecting the pressure dependency of the inactivation rate constant;. An increase in pH from 6.5 to 8, on the other hand, did on ly marginally affect the pressure stability of the enzyme. Mushroom PPO at pH 6.5 was markedly sensitized toward pressure by the presence of 2.5 mM 4- hexylresorcinol and slightly stabilized by the presence of 5 mM EDTA. The p resence of 5 mM glutathione, sodium chloride, or benzoic acid caused no sig nificant alteration of the enzyme pressure stability. Only in the presence of 4-hexylresorcinol, significant changes of the activation volume and z(p) value were noticed.