Table 4. Apparent kinetic parameters of wild-type CtXR and mutants thereof for the reduction of polyhydroxylated aldehyde substrates.
Abbreviation: nd, not determined.
| Value | |||||
|---|---|---|---|---|---|
| Parameter | Enzyme… | Wild-type | N309D | N309A | D50A |
| DL-Glyceraldehyde (25%†) | |||||
| Km (mM) | 3.5 | 35 | 54 | nd | |
| kcat (s−1) | 7.8 | 2.3 | 4.2 | nd | |
| 103×(kcat/Km)′* (M−1·s−1) | 8.9 | 0.3 | 0.3 | nd | |
| D-Glucose (0.0024%†) | |||||
| Km (mM) | 236 | – | – | 486 | |
| kcat (s−1) | 4.8 | – | – | 2.2 | |
| 103×(kcat/Km)′* (M−1·s−1) | 833 | 8.3 | 8.3 | 188 | |
| D-Galactose (0.02%†) | |||||
| Km (mM) | 208 | 264 | – | 244 | |
| kcat (s−1) | 11 | 0.3 | – | 3.3 | |
| 103×(kcat/Km)′* (M−1·s−1) | 265 | 5.5 | 9.0 | 70 | |
| 2-Deoxy-D-galactose (0.03%†) | |||||
| Km (mM) | 742 | 187 | 178 | – | |
| kcat (s−1) | 2.1 | 0.2 | 0.9 | – | |
| 103×(kcat/Km)′* (M−1·s−1) | 9.3 | 3.7 | 17 | 6.3 | |
* kcat/Km′ values are corrected for the proportion of open-chain free aldehyde in aqueous solution (shown in parentheses and indicated by
† [34]).