Figure 3

Characterization of Est_p6. (A) Effect of pH on Est_p6 activity, measured at 50°C for 3 min in 50 mM buffer. The buffers used were sodium citrate (●), MOPS (○), Tris–HCl (▲), CHES (□), and CAPS (■). (B) Effect of pH on stability of Est_p6, treated at 0°C for 0–4000 min in various buffers. Residual enzyme activity was measured at 50°C in 50 mM Tris–HCl buffer, pH 8.60. (C) Effect of temperature on Est_p6 activity, measured for 3 min in 50 mM Tris–HCl buffer, pH 8.60. (D) Effect of temperature on Est_p6 stability. Est_p6 was incubated in 50 mM Tris–HCl buffer, pH 8.60, at 30, 40, or 50°C for various durations, and residual activity was measured at 50°C for 3 min. (E) Effect on Est_p6 activity of various metal ions as indicated, at concentrations of 0.5, 1, and 5 mM. (F) Effect on Est_p6 activity of various detergents and inhibitors at concentrations of 1 and 5 mM. The compounds tested were non-ionic surfactants (Tween 20, Tween 80, Triton X-100), ionic surfactants (SDS, CTAB), inhibitors (EDTA, PMSF), and a reducing agent (DTT). The maximal activity was defined as 100% and the relative activity is shown as a percentage of maximal activity (A-D), the 100% activity is shown as the activity that measured under standard conditions without metal cation or organic solvent (E, F).