Table 2.

Kinetic parameters for TLA-1 β-lactamase for each β-lactam antibiotic and inhibitora

SubstrateKm (μM)RelativeVmaxbRelativeVmax/Km bKi (μM)
Benzylpenicillin36 ± 5.5c 100100
Cephalothin23 ± 4.183130
Cephaloridine102 ± 1323884
Ceftazidime171 ± 3811022
Cefotaxime31 ± 9.897113
Cefepime303 ± 63445
Aztreonam58 ± 193824
CefoxitinNDd NDND
ImipenemNDNDND
Clavulanic acid3.36
Sulbactam5.37
Tazobactam0.69
  • a Measurements were carried out in 100 mM phosphate buffer (pH 7.0) at room temperature.

  • b Values relative to the value for benzylpenicillin, which was set at 100.

  • c Standard deviations are for triplicate determinations.

  • d ND, not detectable; rates were too slow.