Table 3.

Kinetic parameters of purified CME-1 enzyme

SubstrateKm(μM)a,bkcat(s−1)akcat/ Km(μM−1 s−1)
Penicillin G3.1 ± 0.21.2 ± 0.070.39
Ampicillin5.1 ± 0.42.9 ± 0.180.57
Carbenicillin7.0 ± 0.42.6 ± 0.170.37
Piperacillin0.12 ± 0.010.23 ± 0.021.92
Nitrocefin25 ± 1.2134 ± 8.05.36
Cephaloridine87 ± 5.774 ± 4.30.85
Cephalothin105 ± 4.4118 ± 6.01.12
Cefuroxime106 ± 4.6102 ± 6.20.96
Cefoxitin NDc NHd
Cefotaxime50 ± 3.027 ± 1.60.54
Ceftazidime511 ± 3668 ± 4.40.13
Cefepime487 ± 3948 ± 2.70.099
ImipenemND NH 
Aztreonam5.0 ± 0.30.23 ± 0.020.046
Carumonam3.6 ± 0.30.17 ± 0.010.047
  • a Values are means ± standard deviations of three measurements.

  • b Determined as Ki when Km was lower than 10 μM.

  • c not determined.

  • d NH, no hydrolysis detected.