TABLE 2

Kinetic parameters of IMP-7 and IMP-51 enzymesa

β-LactamIMP-7IMP-51
Km (μM)bkcat (s−1)bkcat/Km (μM−1 s−1)Km (μM)bkcat (s−1)bkcat/Km (μM−1 s−1)
Ampicillin116 ± 188.5 ± 1.30.02872 ± 1533.5 ± 0.60.004
Penicillin G212 ± 1817.5 ± 1.30.081976 ± 1884.6 ± 0.70.0048
AztreonamNHcNHNHNHNHNH
Cefepime58 ± 31.2 ± 0.10.02056 ± 41.4 ± 0.10.025
Cefmetazole47 ± 53.7 ± 0.10.0781.8 ± 0.42.78 ± 0.011.5
Cefotaxime12 ± 21.7 ± 0.10.155.7 ± 1.84.4 ± 0.20.93
Cefoxitin120 ± 134.9 ± 0.20.0412.2 ± 0.61.91 ± 0.020.88
Cefpirome57 ± 52.0 ± 0.10.035182 ± 253.4 ± 0.40.019
Ceftazidime19 ± 30.34 ± 0.010.01835 ± 40.03 ± 0.010.0085
Cephradine55 ± 812 ± 10.2275 ± 210.80 ± 0.080.011
Doripenem46 ± 72.7 ± 0.20.05961 ± 710.7 ± 0.40.18
Imipenem104 ± 135.0 ± 0.20.048312 ± 295.5 ± 0.30.018
Meropenem59 ± 80.99 ± 0.070.01751 ± 82.7 ± 0.10.053
Panipenem40 ± 54.0 ± 0.20.099230 ± 710.6 ± 0.20.046
Moxalactam57 ± 64.6 ± 0.20.08124 ± 35.0 ± 0.10.21
  • a The proteins were initially modified by a His tag, which was removed after purification.

  • b Km and kcat values represent the means ± standard deviations from three independent experiments.

  • c NH, no hydrolysis was detected at substrate concentrations up to 1 mM and enzyme concentration up to 700 nM.