Table 2.
Arrhenius parameters for rate constants and KIEs at each pressure investigated.[a]
| Entry | Enzyme | Pressure (bar) | Ea(H) (kcal/mol) | ΔEa (kcal/mol)[b] | ln(AH) |
|---|---|---|---|---|---|
| 1 | WT | 1 | 2.63(0.33) | 1.19(0.42) | 10.2(0.6) |
| 2 | 344 | 5.65(0.46) | 0.81(0.65) | 15.5(0.9) | |
| 3 | 688 | 6.03(1.17) | 1.02(1.12) | 15.7(2.3) | |
|
|
|||||
| 4 | 1034 | 7.62(0.63) | 0.43(0.79) | 18.9(1.2) | |
|
| |||||
| 5 | I553V | 1 | 3.06(0.31) | 2.82(0.41) | 10.5(0.5) |
| 6 | 344 | 3.09(0.40) | 2.85(0.61) | 10.6(0.7) | |
| 7 | 688 | 4.90(0.46) | 2.93(0.69) | 13.7(0.8) | |
|
|
|||||
| 8 | 1034 | 8.01(0.55) | 0.89(1.08) | 19.0(1.0) | |
|
| |||||
| 9 | L546A | 1 | 3.90(0.20) | 3.02(0.51) | 8.7(0.4) |
| 10 | 344 | 4.86(0.35) | 3.36(0.37) | 10.4(0.7) | |
| 11 | 688 | 5.37(0.48) | 2.95(0.52) | 11.4(0.8) | |
|
|
|||||
| 12 | 1034 | 6.67(0.69) | 2.32(0.78) | 13.7(1.3) | |
|
| |||||
| 13 | L754A | 1 | 2.79(0.20) | N.D.[c] | 3.4(0.1) |
| 14 | 344 | 4.31(0.60) | N.D.[c] | 6.5(1.0) | |
| 15 | 688 | 3.64(0.39) | N.D.[c] | 6.0(0.7) | |
|
|
|||||
| 16 | 1034 | 4.06(0.36) | N.D.[c] | 7.1(0.6) | |
[a]
The obtained values for Ea and ΔEa are slightly different, with larger errors, compared to the previous report,[6] probably due to the narrower temperature window herein (15–35°C) compared to a range of 5–50°C in previous studies. In the present study, protein instability at high pressure precluded measurements below 15°C or higher than 35°C.
[b]
ΔEa= Ea(D)− Ea(H).
[c]
The Ea(D) values of L754A under varied pressure were experimentally inaccessible.