TABLE 2.
Kinetic constants for turnover of β-lactam substrates with the E. cloacae P99 β-lactamase and its Leu-293-Pro mutant derivativea
| β-Lactamase | Km (μM) | kcat (s−1) | kcat/Km (M−1 s−1) |
|---|---|---|---|
| LOR | |||
| Wild type | 68 ± 8 | 826 ± 62 | (12 ± 1) × 106 |
| Leu-293-Pro | 60 ± 6 | 126 ± 9 | (2.1 ± 0.2) × 106 |
| CAZ | |||
| Wild type | 15 ± 2 | 0.013 ± 0.001 | (9 ± 1) × 102 |
| Leu-293-Pro | 10 ± 3 | 0.10 ± 0.01 | (10 ± 3) × 103 |
| FEP | |||
| Wild type | 100 ± 16 | 0.5 ± 0.1 | (0.47 ± 0.03) × 104 |
| Leu-293-Pro | 24 ± 2 | 3.1 ± 0.2 | (13 ± 1) × 104 |
a
Abbreviations: LOR, cephaloridine; CAZ, ceftazidime; FEP, cefepime.