TABLE 2

Kinetic parameters of NDM-14 and NDM-1 enzymesa

β-LactamNDM-14NDM-1
Km (μM)bkcat (s−1)bkcat/Km (μM−1s−1) ratioKm (μM)bkcat (s−1)bkcat/Km (μM−1s−1) ratio
Ampicillin80 ± 14102 ± 71.28154 ± 10182 ± 51.18
Penicillin G186 ± 9230 ± 101.2458 ± 5142 ± 82.45
Cefotaxime46 ± 563 ± 41.3726 ± 449 ± 31.88
Ceftazidime72 ± 416 ± 10.2251 ± 322 ± 10.43
Cefuroxime44 ± 215 ± 10.3431 ± 120 ± 10.65
AztreonamNHcNHNHNHNHNH
Imipenem90 ± 442 ± 20.47108 ± 558 ± 30.54
Meropenem53 ± 260 ± 31.1369 ± 772 ± 91.04
  • a The proteins were initially modified by adding a His tag, which was removed after purification.

  • b Values are means from three independent experiments ± standard deviations.

  • c NH, no hydrolysis was detected under conditions with substrate concentrations of up to 1 mM and enzyme concentrations of up to 700 nM.