Table 2.
Kinetic parameters of AmpC β-lactamase
| β-Lactamase | Antibacterial agent | kcat (s−1)a | Km or Ki (μM)a | kcat/Km or Ki (μM−1 s−1) |
|---|---|---|---|---|
| AmpC (P. aeruginosa) | cefiderocol | NHb | 214 ± 49.6c | ND |
| ceftazidime | NHb | 5.3 ± 1.0c | ND | |
| cefepime | NHb | 12.2 ± 0.1c | ND | |
| cefalotin | 95.4 ± 9.3 | 24.5 ± 3.2 | 3.89 | |
| meropenem | NHb | 1.7 ± 0.4c | ND | |
| P99 (E. cloacae) | cefiderocol | NHb | >1700d | ND |
| ceftazidime | (2.7 ± 0.49) × 10−3 | 1.8 ± 0.099c | 0.0015 | |
| cefepime | 0.69 ± 0.028 | 210 ± 21 | 0.0033 | |
| cefalotin | 86 ± 1.5 | 5.8 ± 0.44 | 15 | |
| meropenem | NHb | 0.26 ± 0.0096c | ND |
NH, no hydrolysis detected; ND, not determined (because no hydrolysis was detected).
a
Each kcat and Km or Ki value is the mean ± SD of three different measurements.
b
Hydrolysis was too weak to determine the kcat value.
c
Ki values were obtained using 100 μM cefalotin.
d
This value was the detection limit of the spectrophotometer and no hydrolysis was observed at this concentration.