Table 2.
Kinetic parameters for GES-18, GES-5, and GES-1 β-lactamasesa
| Antibiotic | GES-18 |
GES-5 |
GES-1 |
||||||
|---|---|---|---|---|---|---|---|---|---|
| kcat (s−1) | Km (μM) | kcat/Km (mM−1 s−1) | kcat (s−1) | Km (μM) | kcat/Km (mM−1 s−1) | kcat (s−1) | Km (μM) | kcat/Km (mM−1 s−1) | |
| Benzylpenicillin | 70 | 400 | 175 | 110 | 430 | 255 | 30 | 120 | 250 |
| Amoxicillin | 7 | 40 | 175 | 13 | 50 | 260 | 13 | 180 | 72 |
| Ticarcillin | 5 | 1,000 | 5 | 5 | 1,600 | 3 | 7 | 1,000 | 7 |
| Piperacillin | 75 | 700 | 100 | 160 | 1,000 | 160 | 8 | 900 | 9 |
| Temocillin | 0.004 | 3,500 | 0.001 | 0.003 | 4,500 | 0.0007 | 0.002 | 4,000 | 0.0005 |
| Cephalothin | 500 | 6,000 | 80 | 900 | 9,000 | 100 | 900 | 5,300 | 170 |
| Cephaloridine | 360 | 4,600 | 70 | 725 | 5,000 | 150 | 540 | 4,600 | 120 |
| Nitrocefin | 100 | 330 | 300 | 260 | 550 | 470 | 380 | 340 | 1100 |
| Cefoxitin | 3.4 | 1,000 | 3 | 4.5 | 860 | 5 | 0.08 | 60 | 1.3 |
| Cefotaxime | >20 | >20,000 | 1 | >28 | >20,000 | 1.4 | 370 | 9,000 | 40 |
| Ceftazidime | >2.5 | >20,000 | 0. 125 | >3 | >20,000 | 0. 15 | >56 | >20,000 | 2.8 |
| Cefepime | >1 | >20,000 | 0.05 | >2 | >20,000 | 0.1 | >16 | > 20,000 | 0. 8 |
| Aztreonam | 0.08 | 3,000 | 0.02 | 0.06 | 1,800 | 0.03 | 4.8 | 4,000 | 1.2 |
| Imipenem | 0.4 | 3.5 | 110 | 0.7 | 4.6 | 150 | 0.007 | 1.5 | 5 |
| Ertapenem | 0.06 | 1.3 | 40 | 0.09 | 1.5 | 60 | 0.003 | 0.4 | 7.5 |
| Meropenem | 0.04 | 1 | 40 | 0.06 | 1 | 60 | 0.0007 | 0.1 | 7 |
a
Data are the means of three independent experiments. Standard deviations were within 10% of the means (with the exception of imipenem, for which they were 30%).