Table 2.
Kinetic constants of OXA-48 variants towards seven β-lactams.
| Constants | OXA-48 WT | S118A | K208A | T209A | R250A | W105A | L158A | |
|---|---|---|---|---|---|---|---|---|
| AMP a | Km (μM) | 86 ± 6 | >800 | 117 ± 8 | 125 ± 9 | 92 ± 7 | 81 ± 9 | 60 ± 11 |
| kcat (s−1) | 817 ± 29 | >10 | 3 ± 0.1 | 164 ± 5.8 | 234 ± 8.1 | 75 ± 3.7 | 20 ± 1.3 | |
| kcat/Km (μM−1 s−1) | 9.5 | 1.7 × 10−2 | 2.6 × 10−2 | 1.3 | 2.5 | 0.9 | 0.3 | |
| CAR | Km (μM) | 57 ± 7 | >500 | 421 ± 36 | 269 ± 23 | 147 ± 19 | 217 ± 12 | 79 ± 6 |
| kcat (s−1) | 311 ± 22 | >1 | 4 ± 0.2 | 323 ± 19 | 160 ± 12 | 127 ± 12 | 18 ± 0.7 | |
| kcat/Km (μM−1 s−1) | 5.5 | 6.6 × 10−3 | 9.5 × 10−3 | 1.2 | 1.1 | 0.6 | 0.2 | |
| PIP | Km (μM) | 96 ± 10 | >500 | 385 ± 12 | 93 ± 20 | 195 ± 35 | 162 ± 38 | 461 ± 91 |
| kcat (s−1) | 197 | >0.4 | 4 ± 0.1 | 61 ± 6.3 | 109 ± 12 | 58 ± 9.1 | 98 ± 14 | |
| kcat/Km (μM−1 s−1) | 2.1 | 3.0 × 10−3 | 1.0 × 10−2 | 0.7 | 0.6 | 0.4 | 0.2 | |
| OXA | Km (μM) | 34 ± 3 | 337 ± 20 | 130 ± 11 | 81 ± 15 | 138 ± 13 | 116 ± 15 | 184 ± 11 |
| kcat (s−1) | 162 ± 5.4 | 1.4 ± 0.1 | 2 ± 0.1 | 52 ± 4.6 | 94 ± 5.2 | 60 ± 4.4 | 20 ± 1.1 | |
| kcat/Km (μM−1 s−1) | 4.8 | 4.2 × 10−3 | 1.5 × 10−2 | 0.6 | 0.7 | 0.5 | 0.1 | |
| IPM | Km (μM) | 4 ± 0.2 | >150 | >150 | 232 ± 87 | 926 ± 48 | 24 ± 2.9 | >150 |
| kcat (s−1) | 6 ± 0.02 | >0.05 | >0.005 | 0.4 ± 0.1 | 4 ± 1.9 | 0.03 ± 0.01 | >1 | |
| kcat/Km (μM−1 s−1) | 1.5 | 7.1 × 10−4 | 3.0 × 10−5 | 1.8 × 10−3 | 2.2 × 10−3 | 1.3 × 10−3 | 1.0 × 10−2 | |
| MEM | Km (μM) | 40 ± 0.3 | >300 | >300 | 60 ± 6.3 | >300 | 65 ± 5.8 | 55 ± 4.9 |
| kcat (s−1) | 0.1 ± 0.01 | >0.02 | >0.01 | 0.1 ± 0.01 | >0.01 | 0.01 ± 0.001 | 0.04 ± 0.001 | |
| kcat/Km (μM−1 s−1) | 2.5 × 10−3 | 6.3 × 10−5 | 3.1 × 10−5 | 1.7 × 10−3 | 7.0 × 10−5 | 1.5 × 10−4 | 7.3 × 10−4 |
a AMP, ampicillin; CAR, carbenicillin; PIP, piperacillin; OXA, oxacillin; IPM, imipenem; MEM, meropenem.