Table 3.

Substrate and inhibitor profiles of purified CTX-M-5 β-lactamase

Substrate or inhibitorkcat (s−1)RelativekcatKm (μM)kcat/Km (mM−1s−1)IC50 (nM)
Substrates
 Benzylpenicillin230100504,600
 Cephaloridine1,5006803504,400
 Cefotaxime21095772,800
 Ceftazidime7.43.344017
 Aztreonam219.373029
 Cefoxitin0.410.18 NCa NC
 Imipenem0.00270.0012NCNC
Inhibitors
 Clavulanic Acid19
 Sulbactam100
 Tazobactam3.3
  • a NC, not calculated (rates were too low to obtain reliable values).