Figure 3. Effects of temperature and pH on SK-4 lipase.

(A) Effects of temperature on lipase activity (○) and thermostability of the lipase (•). For effect of temperature, lipase activity assay was performed at various temperatures in 50 mM sodium phosphate buffer (pH 7.0) for 30 min. For thermostability, lipase was preincubated at various temperatures for 30 min. Remaining lipase activity was examined at 65°C for 30 min in 50 mM Tris-HCl buffer (pH 8.5). The line was fitted by using the Eyring-Arrhenius equation. (B) Effects of pH on lipase activity (○) and pH stability of lipase (•). For effect of pH, lipase activity assay was performed with various buffers at 30°C for 30 min using p-nitrophenyl-palmitate as a substrate. For pH stability, lipase was preincubated in various pH buffers at 30°C for 15 h and then pH of the buffer was adjusted to 8.5. The remaining enzyme activity was examined at 65°C for 30 min using p-nitrophenyl-palmitate as a substrate. The line was fitted by Henderson- Hasselbalch equation.