Table 1.
Apparent kinetic constants for the reaction catalyzed by CysE in the absence and presence of CysK at fivefold molar excess over CysE. When acetyl-CoA was the varied substrate the concentration of L-Ser was 20 mM. When L-Ser was the varied substrate, the concentration of acetyl-CoA was 0.25 mM. The concentration of CysE for the calculation of kcat is based on the hexameric complex.
| Varied substrate | Kinetic constants | −CysK | +CysK |
|---|---|---|---|
| Acetyl-CoA | KM (mM) | 1.4 ± 0.4 | 0.8 ± 0.2 |
| kcat (s−1) | 306 ± 35 | 416 ± 38 | |
| kcat/KM (mM−1·s−1) | 212 ± 83 | 501 ± 148 | |
| L-Ser | KM (mM) | 1.7 ± 0.7 | 1.1 ± 0.4 |
| kcat (s−1) | 228 ± 60 | 228 ± 34 | |
| kcat/KM (mM−1·s−1) | 134 ± 90 | 207 ± 106 | |
| Ki,L-Ser (mM) | 3.7 ± 1.4 | 16 ± 5 |