Table 2

Kinetic parameters of β-lactamases IMP-7, IMP-11, IMP-43, and IMP-44 with various substrates

SubstrateKm (μM)akcat (s−1)akcat/Km (μM−1 · s−1)a
IMP-7IMP-43IMP-11IMP-44IMP-7IMP-43IMP-11IMP-44IMP-7IMP-43IMP-11IMP-44
Penicillin G207 ± 193176 ± 236574 ± 18482 ± 5325.3 ± 0.764 ± 336 ± 214 ± 10.120.020.0630.029
Ampicillin180 ± 10494 ± 40230 ± 21627 ± 809.1 ± 0.63.5 ± 0.27.4 ± 0.611 ± 10.0510.00720.0320.017
Cephradine27 ± 269 ± 539 ± 4119 ± 88.0 ± 0.310.3 ± 0.814.6 ± 0.714.1 ± 0.20.290.150.380.12
Cefoxitin33 ± 155 ± 54.4 ± 1.253 ± 54.18 ± 0.053.48 ± 0.053.2 ± 0.112 ± 10.130.0620.760.22
Cefotaxime24 ± 26.8 ± 0.935 ± 427 ± 31.88 ± 0.077.2 ± 0.14.3 ± 0.244 ± 10.081.10.121.6
Ceftazidime59 ± 414 ± 229 ± 363 ± 40.89 ± 0.051.9 ± 0.11.33 ± 0.095.6 ± 0.20.0150.140.0460.089
Cefepime50 ± 630 ± 440 ± 564 ± 51.34 ± 0.044.6 ± 0.12.00 ± 0.0419.4 ± 0.70.0270.160.050.31
AztreonamNHbNHNHNHNHNHNHNHNHNHNHNH
Doripenem63 ± 559 ± 7101 ± 10257 ± 276.8 ± 0.210.0 ± 0.411.3 ± 0.6589 ± 400.110.170.112.3
Imipenem254 ± 20268 ± 23142 ± 7119 ± 1120 ± 149 ± 219.2 ± 0.5165 ± 50.0780.180.131.4
Meropenem59 ± 724 ± 250 ± 5137 ± 162.6 ± 0.28.2 ± 0.35.9 ± 0.2335 ± 130.0440.340.122.5
  • a The Km and kcat values are the means ± standard deviations from three independent experiments.

  • b NH, no hydrolysis detected with substrate concentrations up to 1 mM and enzyme concentrations up to 700 nM.