TABLE 4.
Kinetic parameters of purified β-lactamases OXA-14 and OXA-935a
| OXA-14 (G157D) |
OXA-935 (G157D, F153S) |
kcat/Km ratio for OXA-935/OXA-14 |
|||||
|---|---|---|---|---|---|---|---|
| Substrate | Km (μM) ± SDb | kcat (s−1) ± SDc | kcat/Km (μM−1 s−1)d | Km (μM) ± SD | kcat (s−1) ± SD | kcat/Km (μM−1 s−1) | |
| Nitrocefin | 11 ± 1 | 68 ± 1 | 6.2 | 19 ± 3 | 3.4 ± 0.3 | 0.18 | 0.029 |
| Penicillin G | 64 ± 16 | 144 ± 11 | 2.2 | 52 ± 10 | 3.4 ± 0.4 | 0.065 | 0.030 |
| Cephalothin | 29 ± 7 | 1.3 ± 0.2 | 0.045 | 49 ± 7 | 0.16 ± 0.01 | 0.0033 | 0.073 |
| Cefotaxime | 50 ± 8 | 1.9 ± 0.2 | 0.038 | 123 ± 78 | 0.90 ± 0.13 | 0.0073 | 0.19 |
| Cefepime | 37 ± 3 | 32 ± 3 | 0.86 | 78 ± 30 | 4.4 ± 0.8 | 0.056 | 0.065 |
| Ceftazidime | 51 ± 18 | 0.034 ± 0.014 | 0.00067 | 17 ± 1 | 0.24 ± 0.02 | 0.014 | 21 |
| Meropenem | >250 | NDe | ND | >250 | ND | ND | ND |
| Imipenem | >250 | ND | ND | >250 | ND | ND | ND |
a
Data represent the mean ± standard deviation (SD) from three independent experiments.
b
Km, Michaelis constant (substrate affinity).
c
kcat, turnover rate.
d
kcat/Km, specificity constant (catalytic efficiency).
e
ND, not determinable due to a low initial rate of hydrolysis.