TABLE 4.
Kinetic parameters of partially purified β-lactamase OXA-62
| Substrate | Km (μM) | Vmax (nmol/min/mg) | Relative Vmaxa (%) | Vmax/Km ratio | Relative Vmax/Kma (%) |
|---|---|---|---|---|---|
| Benzylpenicillin | 28 ± 2.3 | 31 ± 0.8 | 100 | 1.1 | 100 |
| Cephaloridine | 3,200 ± 500 | 14 ± 2.0 | 44 | 0.004 | 0.36 |
| Ampicillin | 160 ± 2.1 | 190 ± 8.0 | 600 | 1.2 | 109 |
| Piperacillin | 13 ± 5.7 | 2.1 ± 0.14 | 6.8 | 0.16 | 14.5 |
| Oxacillin | 35 ± 5.5 | 67 ± 2.5 | 220 | 1.9 | 172 |
| Ticarcillinb | NDc | ≤0.31 | ≤1.0 | ND | ND |
| Imipenem | 13 ± 1.4 | 0.044 ± 0.0 | 0.14 | 0.003 | 0.27 |
| Meropenem | 8.0 ± 2.8 | 0.058 ± 0.0 | 0.18 | 0.007 | 0.64 |
| Cefoxitin | 68 ± 1.4 | 0.23 ± 0.016 | 0.74 | 0.003 | 0.27 |
| Ceftazidimeb | ND | ≤0.01 | ≤0.026 | ND | ND |
| Cefotaximeb | ND | ≤0.01 | ≤0.036 | ND | ND |
| Aztreonamb | ND | ≤0.50 | ≤1.6 | ND | ND |
a
The benzylpenicillin value was taken as 100%.
b
Vmax was estimated due to slow hydrolysis.
c
ND, not determined. Hydrolysis was too slow to determine the Km.