Table 4.
Effects of organic solvents on EST4 activity
| Organic solvents | log P a | Residual activity (%)b at concentration (%, v/v) of | ||
|---|---|---|---|---|
| 20 | 50 | 100 | ||
| Control | – | 100.0 ± 2.1 | 100.0 ± 3.8 | 100.0 ± 0.5 |
| DMSO | −1.3 | 82.8 ± 1.7 | 61.7 ± 8.6 | 0.6 ± 1.5 |
| DMF | −1.0 | 92.1 ± 2.5 | 19.4 ± 4.2 | 5.8 ± 2.0 |
| Methanol | −0.76 | 90.6 ± 9.4 | 23.2 ± 1.8 | 1.3 ± 3.2 |
| Ethanol | −0.24 | 102.0 ± 7.7 | 0.5 ± 2.4 | 4.9 ± 2.1 |
| Acetone | −0.23 | 53.1 ± 6.4 | NDc | 85.2 ± 1.3 |
| Acetonitrile | −0.15 | 96.2 ± 2.7 | 7.8 ± 1.4 | 89.0 ± 4.3 |
| Isopropanol | 0.1 | 81.3 ± 7.9 | ND | 97.0 ± 0.9 |
| Benzene | 2.0 | 37.9 ± 3.3 | 76.1 ± 4.7 | 92.8 ± 4.3 |
| Toluene | 2.5 | 63.5 ± 1.6 | 88.1 ± 4.0 | 90.1 ± 0.5 |
| Cyclohexane | 3.2 | 80.1 ± 2.7 | 92.7 ± 5.9 | 99.7 ± 1.8 |
| n-hexane | 3.5 | 53.1 ± 4.6 | 95.3 ± 10.6 | 98.6 ± 0.5 |
| n-heptane | 4.0 | 66.1 ± 2.8 | 96.9 ± 5.6 | 97.6 ± 1.3 |
| Isooctane | 4.5 | 85.5 ± 5.4 | 90.0 ± 10.9 | 98.4 ± 1.0 |
alog P value is the partition coefficient of an organic solvent between water and n-octanol phases
bAfter incubating EST4 for 12 h in different organic solvents, the residual enzymatic activity was measured in 100 mM Tris–HCl buffer (pH 8.0) at 30 °C using p-NP butyrate as the test substrate. An enzyme sample incubated in buffer only was used as the measure of 100 % activity
c ND not detectable