TABLE 3.

Steady-state kinetic parameters for the hydrolysis of β-lactam substrates of VIM-2 and its A64W mutanta

Substratekcat (s−1)Km (μM)kcat/Km (μM−1 s−1)
VIM-2VIM-2 A64WIMP-1IMP-1 W64AVIM-2VIM-2 A64WIMP-1IMP-1 W64AVIM-2VIM-2 A64WIMP-1IMP-1 W64A
Ampicillin12550200b86b90300320b1,250b1.40.170.63b0.07b
Cephalothin13013532c>250c1165c>500c12226.4c0.31c
Cefoxitin15d940133451.23.00.9
Cefuroxime8158204370.43.70.22
Cefotaxime702613.4981272.8615.83.74.81.5
Ceftazidime3.60.787240440.050.0180.18
Cefepime>40>507>400>400110.10.120.66
Nitrocefin77027013070018108.21604327144.3
Imipenem34606867921251203.82.92.70.55
Meropenem56522102.53.00.5
  • a Kinetic parameters were determined using the experimental conditions described previously for wild-type VIM-2 (4). Data for IMP-1 and its W64A mutant are shown for comparison (17). Data for WT IMP-1 and cefuroxime, ceftazidime, cefepime, and meropenem are from reference 11. Standard deviations were below 10%.

  • b Data for benzylpenicillin.

  • c Data for cephaloridine.

  • d —, data not available.