Table 2.

Kinetic properties of IMP-4 β-lactamase from isolate 74510

SubstrateRelative Vmax(%)aKm (μM)
Benzylpenicillin100365
Ampicillin52575
Piperacillin8144
Carbenicillin621,000
Oxacillin307420
Cephaloridine8132
Cephalothin11171
Cefuroxime4652
Cefotaxime918
Ceftazidime728
Imipenem5342
Meropenem812
Aztreonam0.001Not measured
  • a Based on a predicted molecular mass of 27,087 and a purity of 80%; based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, ak cat of 27.5 s−1 was estimated for IMP-4 against benzylpenicillin.