Table 3.

Kinetic parameters and inhibition profile of SMB-1a

Substrate or chelating agentKm (μM)kcat (s−1)kcat/Km (M−1·s−1)Relative kcat/KmdIC50 (μM)
Ampicillin1022472.4 × 106100
Piperacillin380681.8 × 1057.5
Cephalothin15281.9 × 10679
Cefuroxime22301.4 × 10658
Cefotaxime35318.9 × 10537
Ceftazidime574.47.7 × 1043.2
Cefepime7472.73.6 × 1030.15
Cefoxitin26391.5 × 10663
AztreonamNHbNDcNDND
Imipenem1335183.9 × 106163
Meropenem1446044.2 × 106175
Dipicolinic acid2.2
1,10-o-Phenanthroline156
EDTA14
  • a Standard deviations for each parameter were below 10%.

  • b NH, no measurable hydrolysis detected with 1 μM enzyme.

  • c ND, not determined.

  • d Relative kcat/Km value was expressed compared to that of ampicillin, which was assigned 100.