Table 3.
Kinetic parameters for amino acid activation by WT and mutant variants of Ec ProRSa
| Ec ProRS | kcat (s−1) | KM (mM) | kcat/KM (mM−1 sec−1) | kcat/KM (relative) | Fold-Decrease | ΔΔG (kcal/mol) |
|---|---|---|---|---|---|---|
| WT | 12.6 ± 4.9 | 0.18 ± 0.03 | 71 | 1.0 | - | - |
| D198A | 6.98 ± 0.37 | 0.33 ± 0.01 | 21 | 0.30 | 3.4 | 0.75 |
| E218Ab | 4.4 ± 2.3 | 3.40 ± 0.68 | 1.3 | 0.02 | 55 | 2.5 |
| E234A | 6.7 ± 1.9 | 1.03 ± 0.25 | 6.5 | 0.09 | 11 | 1.5 |
| H302A | 7.3 ± 1.9 | 0.22 ± 0.04 | 33 | 0.46 | 2.1 | 0.46 |
| N305A | 0.61 ± 0.18 | 0.45 ± 0.18 | 1.4 | 2.0 × 10−2 | 51 | 2.4 |
| G412A | 12.8 ± 0.57 | 0.300 ± 0.003 | 43.0 | 0.61 | 1.6 | 0.29 |
| F415A | 0.131 ± 0.010 | 0.76 ± 0.29 | 0.17 | 2.4 × 10−3 | 400 | 3.7 |
| H302A/G412A | 10.7 ± 0.80 | 0.62 ± 0.26 | 17 | 0.24 | 4. 2 | 0.88 |
| N305A/G412A | ND | ND | ND | - | - | - |
| E218A/N305A | ND | ND | ND | - | - | - |
a
Results are the average of 3 trials with the standard deviation indicated. ΔΔG was calculated according to the equation ΔΔG = −RT ln (fold-decrease of kcat/KM), where R is the gas constant, 1.986 cal K−1 mol−1 and T is 310 K. ND indicates not detectable under the experimental conditions used.
b
Data is from reference (16).