TABLE 2.
Kinetic parameters of PDC variants with different β-lactam substratesa
| β-Lactam | PDC-3 |
PDC-461 |
PDC-462 |
PDC-463 |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Km (μM) | kcat (s−1) | kcat/Km (mM−1 s−1) | Km (μM) | kcat (s−1) | kcat/Km (mM−1 s−1) | Km (μM) | kcat (s−1) | kcat/Km (mM−1 s−1) | Km (μM) | kcat (s−1) | kcat/Km (mM−1 s−1) | |
| CAZ | 57.4 ± 39.3 | 0.0105 ± 0.000778 | 0.183 ± 0.138 | 93.1 ± 40.5 | 0.465 ± 0.00707 | 4.99 ± 2.25 | 23.1 ± 1.98 | 0.122 ± 0.0103 | 5.28 ± 0.897 | 55.0 ± 26.5 | 0.133 ± 0.0106 | 2.41 ± 1.35 |
| PIP | 18.6 ± 6.84 | 2.86 ± 1.93 | 154 ± 160 | 105 ± 1.55 | 0.145 ± 0.00705 | 1.38 ± 0.0871 | 9.86 ± 3.23 | 1.44 ± 0.0574 | 146 ± 5.38 | 54.5 ± 34.8 | 0.801 ± 0.216 | 14.7 ± 1.33 |
| IMP | 10.4 ± 2.96 | 0.0159 ± 0.00872 | 1.53 ± 1.27 | 33.9 ± 21.4 | 0.00725 ± 0.00247 | 0.214 ± 0.208 | 37.3 ± 3.62 | 0.0389 ± 0.00512 | 1.03 ± 0.238 | 35.9 ± 4.76 | 0.0130 ± 0.00141 | 0.362 ± 0.0872 |
| CTZb | ND | ND | 0.040 ± 0.0092 | ND | ND | 6.1 ± 1.3 | ND | ND | 0.66 ± 0.14 | ND | ND | 0.33 ± 0.055 |
a
Kinetic parameters were determined for ceftazidime (CAZ), piperacillin (PIP), imipenem (IMP), and ceftolozane (CTZ). Two independent experiments were carried out, and results are expressed as means ± SEM.
b
Due to the low hydrolysis of ceftolozane, kcat/Km values were obtained from Lineweaver-Burk plots. ND, not determined.