TABLE 3.
Substrate and inhibitor profiles of purified FOX-5 β-lactamase
| Compound | kcat (S−1) | Relative kcat | Km (μM) | kcat/Km (mM−1 s−1) | IC50 (μM) |
|---|---|---|---|---|---|
| Substrates | |||||
| Cephaloridine | 790 ± 52 | 100 | 1,300 ± 58 | 610 | |
| Cephalothin | 870 ± 15 | 110 | 71 ± 5.3 | 12,000 | |
| Benzylpenicillin | 11 ± 0.3 | 1.4 | 9.2 ± 0.6 | 1,200 | |
| Cefoxitin | 0.7 ± 0.04 | 0.09 | 0.85 ± 0.09 | 820 | |
| Cefepime | 0.6 ± 0.1 | 0.08 | 86 ± 2 | 7.0 | |
| Cefpodoxime | 1.5 ± 0.04 | 0.19 | 2.3 ± 0.5 | 650 | |
| Ceftazidime | <0.08 | <0.01 | NDa | ND | |
| Cefotaxime | 0.08 | 0.01 | ND | ND | |
| Aztreonam | <0.08 | <0.01 | ND | ND | |
| Inhibitors | |||||
| Clavulanic acid | >45 | ||||
| Tazobactam | 28 ± 3 | ||||
| Aztreonam | 0.0002b |
a
ND, not determined.
b
Ki was 1.6 nM.