Table 2.
Steady-state enzyme kinetics of tScCBS and HsCBS for both the canonical and the alternative H2S-generating reactions
| Kinetic parameter | tScCBS | HsCBS – SAM | HsCBS + SAM |
|---|---|---|---|
| Ser + Hcy → Cth + H2O | |||
| Km (mM) | 2.0 ± 0.4 | 0.8 ± 0.1 | 1.6 ± 0.2 |
| Vmax (μmol·h−1·mg−1) | 250.7 ± 13.4 | 37.2 ± 1.5 | 156.3 ± 7.6 |
| kcat (s−1) | 2.7 ± 0.1 | 0.63 ± 0.06 | 2.7 ± 0.1 |
| kcat/Km (s−1·mM−1) | 1.34 | 0.79 | 1.66 |
| Cys + Hcy → Cth + H2S | |||
| Km (mM)a | 2.5 ± 0.2 | 1.0 ± 0.4 | 2.1 ± 0.5 |
| Vmax (μmol·h−1·mg−1)a | 161.5 ± 4.5 | 20.1 ± 1.7 | 97.2 ± 7.1 |
| kcat (s−1)a | 1.7 ± 0.1 | 0.34 ± 0.02 | 1.66 ± 0.03 |
| kcat/Km (s−1·mM−1)a | 0.69 | 0.34 | 0.79 |
| Km (mM)b | 6.7 ± 1.5 | 5.0 ± 0.9 | 11.1 ± 0.8 |
| Vmax (μmol·h−1·mg−1)b | 317.0 ± 24.1 | 30.8 ± 1.9 | 113.3 ± 4.0 |
| kcat (s−1)b | 3.4 ± 0.3 | 0.52 ± 0.04 | 1.93 ± 0.06 |
| kcat/Km (s−1·mM−1)b | 0.51 | 0.11 | 0.17 |
aCBL-LDH coupled-coupled assay
bAzMC assay