TABLE 3.

Steady-state kinetic parameters for representative class A carbapenemasesa

SubstrateSME-1NMC-AIMI-1KPC-2GES-4
kcat (s−1)Rel kcat (%)Km (μM)kcat/Kmkcat (s−1)Rel kcat (%)Km (μM)kcat/Kmkcat (s−1)Rel kcat (%)Km (μM)kcat/Kmkcat (s−1)Rel kcat (%)Km (μM)kcat/Kmkcat (s−1)Rel kcat (%)Km (μM)kcat/Km
Cephaloridine9801007701.32,820100185152,0001001,0701.95301005101.04901002,2000.22
Benzylpenicillin191.9171.12609.2289.3361.8640.566312302.1130271600.81
Imipenem104112020.511,040379211894.51700.52315.8900.340.380.0784.70.081
Meropenem8.90.91130.68120.434.42.7100.5260.383.60.68130.28NANANANA
Ceftazidime<0.07<0.01NDND4.70.17900.0520.00680.000342700.0000250.490.0922300.00212.50.511,5000.0017
Cefotaxime<0.98<0.10NDND286109560.303.40.171900.018173.21000.17173.47000.024
CefepimeNANANANANANANANANANANANA122.35400.022NANANANA
Cefoxitin<0.15<0.02NDND5.00.18930.0530.30.015450.00670.950.181400.006885178100.11
Aztreonam108112600.42707251255.7512.6930.5566124200.16NDHNDNDND
  • a References: SME-1, 179; NMC-A, 124; IMI-1, 183; KPC-2, 246; GES-4, 219. Abbreviations: Rel kcat, kcat relative to that of cephaloridine; ND, not determinable; NA, no data available; NDH, no detectable hydrolysis.