Figure 5

Biochemical characterization of Est_p1. (A) Effect of pH on Est_p1 activity. Est_p1 activity was measured at 40°C for 3 min in 50 mM buffer, at various pH levels. Values are shown as percentage of maximal activity, defined as 100%. Buffers used were sodium citrate (●), MOPS (○), Tris-HCl (▲), CHES (□), and CAPS (■). (B) Effect of pH on stability of Est_p1. Est_p1 was treated at 0°C for 90 min and 400 min in various buffers at various pH levels. Residual enzyme activity was measured at 40°C in 50 mM Tris-HCl buffer, pH 8.57. Values are shown as percentage of original activity (measured in the same buffer and pH, but without incubation at 0°C), defined as 100%. (C) Effect of temperature on Est_p1 activity. Activity was measured at various temperatures as indicated, for 3 min in 50 mM Tris-HCl buffer, pH 8.57. Values are shown as percentage of maximal activity, defined as 100%. The inset shows the temperature dependence as an Arrhenius plot. (D) Effect of temperature on stability of Est_p1. The enzyme was incubated in 50 mM Tris-HCl buffer, pH 8.57, at various temperatures, for 120 min, and residual activity was measured at 40°C for 3 min at 15 min intervals. Residual activity was expressed in Panel B.