Fig. 3

Effects of temperature and pH on the recombinant CE1 activity. a Effect of temperature (22–55 °C) on CE1 activity at pH 6.5. b Effect of pH (5.5–9.0) on CE1 activity at 40 °C. c Themostability: 0.8 μg purified enzyme in 100 μl mixed buffer of 100 mM citrate-phosphate (pH 6.5) was pre-incubated for various times at 40 °C (black square), 45 °C (black circle), and 50 °C (black up-pointing triangle) in the absence of substrate. The activity of the enzyme without pre-incubation was defined as 100 %. d Stability at different pH values: 0.8 μg purified enzyme in 100 μl mixed buffer of 100 mM citrate-phosphate (pH 5.5–8.0) and 100 mM barbitone buffer (pH 8.0–9.0) was pre-incubated for 1 h at 40 °C in the absence of substrate. Full activity was determined at each pH value. The initial activities were determined at pH 6.5 and defined as 100 %. The substrate was pNP butyrate (1 mM)