Fig. 4

Effect of temperature and pH on enzyme activity and stability of WT and mutant. a The effect of temperature on enzyme activity. The temperature-activity profile was measured at a temperature range of 0 to 80 °C in 50 mM Tris–HCl buffer (pH 8.5). Activity value obtained at 10 °C was defined as 100 %. b Temperature stability. The WT and mutant enzyme was incubated at 45 (○ WT; ● 1-D5), 50 (□ WT; ■ 1-D5) and 55 °C (▼ WT; ▲ 1-D5) for various time intervals and the residual activity was measured. The specific activity without incubation was taken as 100 %. c The effect of pH on enzyme activity. The pH-activity profile was determined in phosphate–citrate buffer (pH 5.0–7.0) and 50 mM Tris–HCl buffer (pH 7.0–10.0) at 10 °C. The activity at pH 8.5 was defined as 100 %. d pH stability. The activity was determined by pre-incubating enzyme solutions in different pHs buffers at 4 °C for 24 h and the residual activity was measured under standard condition. The residual activity after treatment with pH 7.0 buffer was shown as 100 %