Figure 6

Effects of pH and temperature on enzyme activities of KmAdhs. a Determination of the optimal pH of the KmAdhs. Enzyme assays were performed at the indicated pH at 40°C using ethanol (closed symbols) and acetaldehyde (open symbols) as substrates. squares, 50 mM citrate-phosphate buffer (pH 4.0-7.0); circles, 50 mM sodium-phosphate buffer (pH 6.0-8.0); triangles, 50 mM Tris–HCl buffer (pH 8.0-9.0); diamonds, 50 mM glycine-NaOH buffer (pH 9.0-10.0). b pH stability of the KmAdhs. Enzyme activity was measured under optimal conditions (50 mM sodium-phosphate buffer of pH 7.0, 40°C) after the enzyme was incubated in the indicated buffers at 4°C for 24 h. c Determination of the optimal temperatures of the KmAdhs. Activity was measured at pH 7.0 (50 mM sodium-phosphate buffer) at the indicated temperatures. d Thermal stability of KmAdhs. Enzyme activity was measured under optimal conditions (50 mM sodium-phosphate buffer of pH 7.0, 40°C) after the enzyme had been incubated at the indicated temperature for 30 min. The error bars represent the standard deviations of triplicate measurements.