Table 2.

Kinetic parameters of the purified IMP-2 enzyme

SubstrateKm (μM)a,bkcat(s−1)akcat/Km (μM−1 s−1)
Ampicillin110 ± 10 (200)c 23 ± 2 (950)0.21 (4.8)
Carbenicillin700 ± 65 (NAd)252 ± 20 (NA)0.36 (0.02)
Nitrocefin95 ± 7 (27)275 ± 22 (63)2.9 (2.3)
Cephaloridine3 ± 0.2 (22)0.8 ± 0.06 (53)0.27 (2.4)
Cefoxitin7 ± 0.5 (8)7 ± 0.7 (16)1.0 (2.0)
Ceftazidime111 ± 9 (44)21 ± 2 (8)0.19 (0.18)
Cefepime7 ± 0.6 (11)4 ± 0.2 (7)0.57 (0.66)
Imipenem24 ± 2 (39)22 ± 2 (46)0.92 (1.2)
Meropenem0.3 ± 0.03 (10)1 ± 0.08 (5)3.3 (0.5)
Aztreonam NDe  NHf ND
  • a Values are means ± standard deviations of three measurements.

  • b Determined as Ki whenKm was lower than 10 μM.

  • c Data in parentheses report the corresponding values previously measured for the IMP-1 enzyme (21).

  • d NA, not available.

  • e ND, not determined.

  • f NH, no hydrolysis detected.