TABLE 3.
Kinetic parameters determined with the TEM-72 β-lactamase purified from E. coli DH5α(pPM-14)
| Substrate | Km (μM)c | kcat (s−1)c | kcat/Km (M−1 s−1) |
|---|---|---|---|
| Benzylpenicillin | 1.6 ± 0.1 | 13 ± 0.8 | 8.1 × 106 |
| Piperacillin | 14 ± 1.2 | 67 ± 2.0 | 4.8 × 106 |
| Nitrocefin | 4.0 ± 0.2 | 14 ± 0.6 | 3.5 × 106 |
| Cephalothin | 5.0 ± 0.1 | 5.0 ± 0.2 | 1.0 × 106 |
| Cephaloridine | 3.7 ± 0.2 | 13 ± 0.6 | 3.5 × 106 |
| Cefazolin | 24 ± 0.9 | 45 ± 1.8 | 1.9 × 106 |
| Cefotaxime | 22 ± 1.2 | 37 ± 1.5 | 1.7 × 106 |
| Ceftazidime | 75 ± 2.0 | 6.0 ± 0.3 | 8.0 × 104 |
| Cefoxitin | NDa | NHb | ND |
| Cefepime | 51 ± 1.8 | 6.4 ± 0.5 | 1.2 × 105 |
| Cefpirome | 246 ± 12 | 25 ± 1.0 | 1.0 × 105 |
| Aztreonam | 2.1 ± 0.1 | 0.5 ± 0.03 | 2.3 × 105 |
a
ND, not determined.
b
NH, no hydrolysis detected.
c
Km and kcat values are the means of three different measurements ± standard deviations.