TABLE 1.
Kinetic parameters of purified IMP-27 and IMP-1
| Antibiotic | IMP-27 |
IMP-1 |
||||
|---|---|---|---|---|---|---|
| Km or Ki (μM) | kcat (s−1) | kcat/Km (M−1 s−1) | Km or Ki (μM) | kcat (s−1) | kcat/Km (M−1 s−1) | |
| Piperacillin | 3,000 ± 390a | NDb | ND | 330 ± 12a | 40 ± 1.5c | 1.2 ×105 |
| Cefotaxime | 24 ± 1.9 | 20 ± 0.66 | 8.6 × 105 | 9.8 ± 1.2 | 16 ± 0.34 | 1.6 ×106 |
| Ceftazidime | 54 ± 4.3 | 0.7 ± 0.03 | 1.3 × 104 | 46 ± 3.8 | 7.4 ± 0.10 | 1.6 ×105 |
| Cefepime | 53 ± 3.6 | 8.1 ± 0.37 | 1.5 × 105 | 42 ± 1.0 | 15 ± 0.36 | 3.6 × 105 |
| Aztreonam | >23,000 NHd | NH | ND | >23,000 NH | NH | ND |
| Imipenem | 310 ± 19a | 34 ± 0.38 | 1.1 × 105 | 28 ± 2.0 | 52 ± 1.5 | 1.8 × 106 |
| Meropenem | 2.3 ± 0.8a | 3.4 ± 0.53 | 1.5 × 106 | 4.3 ± 0.7 | 8.2 ± 0.71 | 2.0 ± 106 |
| Nitrocefin | 36 ± 3.1 | 370 ± 15 | 1.0 × 107 | 3.9 ± 0.37 | 270 ± 17 | 7.0 ×107 |
a
The Km values were measured as Ki with nitrocefin as the reporter substrate.
b
ND, not determined.
c
The kcat values were derived from initial rate measurements at more than 5 times higher than the concentration of Ki.
d
NH, no hydrolysis detected.