Table 3.

Kinetic parameters of the purified β-lactamase CTX-M-93 compared to those of CTX-M-27a

SubstrateCTX-M-93CTX-M-27b
kcat (s−1)Km (μM)kcat/Km (μM−1 s−1)Mean kcat (s−1) ± SDMean Km (μM) ± SDkcat/Km (μM−1 s−1)
Penicillin G0.0722.50.00311 ± 0.56 ± 0.21.8
AmoxicillinNDNDND5 ± 1.010 ± 0.40.5
TicarcillinNDNDND1 ± 0.313 ± 0.30.07
PiperacillinNDNDND9 ± 0.58 ± 0.31.1
Cefalothin1.8330.06232 ± 30.083 ± 1.02.8
Cephaloridine1.4510.03NTNTNT
Cefuroxime0.2341.230.00879 ± 4.045 ± 2.01.75
Cefotaxime0.6670.009113 ± 15.0150 ± 8.00.75
Ceftazidime2.525.50.13 ± 0.3330 ± 22.00.009
AztreonamNDNDND0.4 ± 0.217 ± 1.00.02
  • a Data are means from three independent experiments. Standard deviations were within 15%. ND, not determinable (the initial rate of hydrolysis was lower than 0.001 μM−1 · s−1); NT, not tested.

  • b Results were described previously by Bonnet et al. (4).