Table 2.

Kinetic and inhibition parameters of the OXA-24 β-lactamasea

AntibioticKm (μM)Vmax (μmol/min/μl)RelativeVmax/Km b Relative hydrolysis ratebIC50(μM)c
Benzylpenicillin65370100100
Cephaloridine395200964
Oxacillin NDd NDND<1
CloxacillinNDNDND<1
MethicillinNDNDND<1
Imipenem2015134
Meropenem77528062
Clavulanic acid50
Sulbactam40
Tazobactam0.5
  • a Kinetic experiments were performed using a protein extract with a specific activity of 13.61 μmol of nitrocefin hydrolyzed/min/μg of protein.

  • b Obtained by normalizing the value of each antibiotic to that for benzylpenicillin (taken as 100).

  • c Nitrocefin was used as the substrate (25 μg/ml) following 10 min of preincubation of enzyme and inhibitor.

  • d ND, hydrolysis not detected.