TABLE 3.
Kinetic parameters for the reduction of Tib and TibS catalyzed by AKR1C isoforms
Steady-state parameters were determined by fluorometric assay. Values are given as means ± S.D. (n > 2). Data for Tib were from Ref. 6. Values for AKR1C3-catalyzed reactions were not determined due to low turnover.
| AKR1C1 | AKR1C2 | AKR1C4 | |
|---|---|---|---|
| Tib | |||
| kcat (min−1) | 0.88 ± 0.06 | 12.7 ± 3.7 | 1.83 ± 0.06 |
| Km (μm) | 0.76 ± 0.13 | 0.87 ± 0.34 | 1.02 ± 0.07 |
| kcat/Km (min−1m−1) | 1.2 × 106 | 1.4 × 107 | 1.8 × 106 |
| Ki (μm) | 0.7 ± 0.29 | ||
| TibS | |||
| kcat (min−1) | 1.9 ± 0.3 | 12.1 ± 2.7 | 1.20 ± 0.03 |
| Km (μm) | 2.5 ± 0.28 | 1.2 ± 0.5 | 0.5 ± 0.1 |
| kcat/Km (min−1m−1) | 7.6 × 105 | 1.0 × 107 | 2.4 × 106 |
| Ki (μm) | 2.1 ± 0.6 |