TABLE 2.
Kinetic parameters of the NDM-1 and NDM-12 enzymesa
| β-Lactam | NDM-1b |
NDM-12b |
||||
|---|---|---|---|---|---|---|
| Km (μM) | kcat (s−1)b | kcat/Km (μM−1 s−1) | Km (μM) | kcat (s−1)b | kcat/Km (μM−1 s−1) | |
| Ampicillin | 231 ± 33 | 249 ± 22 | 1.1 | 126 ± 4 | 136 ± 2 | 1.1 |
| Aztreonam | NHc | NH | NH | NH | NH | NH |
| Cefepime | 162 ± 7 | 31 ± 1 | 0.19 | 103 ± 6 | 11.1 ± 0.2 | 0.11 |
| Cefotaxime | 102 ± 16 | 137 ± 7 | 1.1 | 45 ± 4 | 38 ± 1 | 0.84 |
| Cefoxitin | 13 ± 1 | 6.7 ± 0.1 | 0.50 | 26 ± 2 | 0.66 ± 0.01 | 0.02 |
| Ceftazidime | 202 ± 7 | 56 ± 1 | 0.28 | 53 ± 4 | 5.7 ± 0.1 | 0.11 |
| Cefradine | 27 ± 3 | 72 ± 1 | 2.7 | 57 ± 4 | 16 ± 1 | 0.28 |
| Doripenem | 201 ± 27 | 114 ± 9 | 0.57 | 88 ± 2 | 53 ± 1 | 0.60 |
| Imipenem | 249 ± 43 | 44 ± 2 | 0.34 | 125 ± 22 | 22 ± 2 | 0.18 |
| Meropenem | 81 ± 10 | 139 ± 10 | 1.7 | 91 ± 8 | 53 ± 2 | 0.58 |
| Moxalactam | 4.5 ± 2.3 | 7.6 ± 0.3 | 2.0 | 67 ± 5 | 6.0 ± 0.2 | 0.09 |
| Penicillin G | 67 ± 6 | 104 ± 1 | 1.6 | 64 ± 8 | 42 ± 2 | 0.66 |
a
The proteins were initially modified by a His tag, which was removed after purification.
b
The Km and kcat values shown represent the means from 3 independent experiments ± standard deviations.
c
NH, no hydrolysis was detected under conditions with substrate concentrations up to 1 mM and enzyme concentrations up to 700 nM.