TABLE 2.
Kinetic constants of PtM3K on four different substratesa
| Substrate | Activity (U · mg−1) | Km (μM) | kcat (s−1) | kcat/Km (s−1 · μM−1) |
|---|---|---|---|---|
| Mevalonate (MVA) | 3 ± 0.1 | 131 ± 18 | 1.9 | 1.5 × 10−2 |
| 3-Hydroxyisovalerate (3-HIV) | 0.17 ± 0.01 | 2,348 ± 574 | 0.1 | 4.25 × 10−5 |
| 3-Hydroxybutyrate (3-HB) | 0.14 ± 0.01 | 3,163 ± 637 | 0.1 | 2.9 × 10−5 |
| 3-Hydroxypropionate (3-HP) | ND | ND | ND | ND |
a
Activity values refer to the rate of ADP formation coupled to NADH oxidation. Values are calculated at 30°C in 50 mM Tris-HCl buffer, pH 7.5, with the addition of 10 mM MgCl2, 20 mM KCl, and 50 μg of pure PtM3K (for MVA, the amount of pure PtM3K added was 10 μg). Assays were done in triplicate, and the means ± standard errors of the means for the kinetic constants are shown. ND, not detected.