Table 2.
Kinetic characterization of the coupled persulfide dioxygenase-persulfide transferase (cPDO-PT) activity of wild-type CstB with various substrates.a
| Substrate |
Km
(x10−3 M) |
Vmax
(μmol TS · min− 1 · mg−1) |
kcat
(s−1) |
kcat/Km
(x10−3 M−1 · s−1) |
Specific activity ([substrate]=1 mM) (μmol TS · min−1 · mg− 1) |
|---|---|---|---|---|---|
| CoASSH | 1.1 ± 0.3 | 23.3 ± 2.5 | 19.3 ± 2.2 | 17.5 ± 5.1 | 11.2 ± 1.2 |
| BSSH | 1.8 ± 0.4 | 24.1 ± 3.0 | 19.7 ± 2.5 | 10.9 ± 2.8 | 8.6 ± 1.1 |
| CSSHb | 20 ± 21 | 34 ± 32 | 28 ± 27 | 1.4 ± 2.0 | 1.5 ± 0.1 |
| GSSHb | 7.8 ± 5.0 | 7.9 ± 4.0 | 6.5 ± 3.3 | 0.8 ± 0.7 | 0.9 ± 0.1 |
a
Conditions: 0.04 μM CstB (protomer), 25 mM MES, 100 mM NaBr, pH 6.0, 25 °C.
b
Very low activity (see Fig. S6) making it difficult to measure Km and Vmax accurately.