Table 3.

Hydrolysis of various β-lactam antibiotics by IMP-6 and IMP-1 type metallo-β-lactamases

SubstrateIMP-6aIMP-1b
kcat(s−1)cKm (μM)ckcat/Km(μM−1 s−1) kcat(s−1)cKm (μM)ckcat/Km(μM−1 s−1)
Penicillin G51 ± 4.9 220 ± 300.23 320 ± 30520 ± 30 0.62
Piperacillin 22 ± 0.31230 ± 31 0.09NDdND 0.72
Cephalothin 374 ± 6.64.7 ± 0.31e79.6 48 ± 421 ± 2 2.4
Cefotaxime55 ± 3.13.8 ± 0.15e14.51.3 ± 0.54 ± 0.50.35
Aztreonam NHfND ND>0.01 >1,000 <0.0001
Imipenem 68 ± 7.0 110 ± 7.5 0.61 46 ± 339 ± 4 1.2
Panipenem 180 ± 19.5 250 ± 210.71 50 ± 5 10 ± 2 0.12
Meropenem32 ± 0.99 7.6 ± 0.21e4.244 ± 6 30 ± 3 1.5
  • a IMP-6 was purified from KU4867.

  • b IMP-1 values were reported by Laraki et al. (22).

  • c Data represent the mean±standard deviation of more than three measurements.

  • d ND, not determined.

  • e Km was obtained as theKi value.

  • f NH, no hydrolysis detected.