Table 1.
Kinetic resolution of dehalogenation of rac-2-CPE and the azide-mediated ring-opening reaction of rac-styrene oxide catalyzed by wild-type HheA and its variants
| Enzyme | Substrate | % conversion (h)a | e.e.(s) (%) | Config.b | e.e.(p) (%) | Config. | E valuec |
|---|---|---|---|---|---|---|---|
| HheA WT | rac-2-CPE | 33 (3) | 11 | R | 22 | S | 1.7 |
| V136Y/L141G variant | rac-2-CPE | 43 (2) | 57 | S | 77 | R | 13 |
| V136Y/L141G/N178A variant | rac-2-CPE | 40 (0.6) | 58 | R | 86 | S | 23 |
| N178A variant | rac-2-CPE | 50 (0.4) | 98 | R | 97 | S | >200 |
| HheA WT | rac-styrene oxide | 7 (0.4)d | 5 | R | 65 | S | 5 |
| N178A variant | rac-styrene oxide | 51 (0.4) | 96 | R | 93 | S | 108 |
The reaction time is indicated in parentheses. All reactions were carried out using the crude extract of the enzymes. The expression levels of HheA and its variants were estimated from SDS-PAGE.
Config., absolute configuration.
E values were calculated from the e.e. for the substrate [e.e.(s)] and that for the product [e.e.(p)] according to the formula E = ln[(1 − e.e.(s))/(1 + e.e.(s)/e.e.(p))]/ln[(1 + e.e.(s))/(1 + e.e.(s)/e.e.(p))].
The concentration of wild-type HheA used in this reaction is 5-fold higher than that of the enzymes used in all other reactions due to its low activity in the ring-opening reaction of styrene oxide with azide.