TABLE 2

Kinetic constants of the four enzymes studied against 10 β-lactam antibacterialsa

β-Lactamkcat (s−1)Km (μM)kcat/Km (μM−1 s−1)
IMP-1-V67AIMP-1 (V67)IMP-1-V67IIMP-10 (F67)IMP-1-V67AIMP-1 (V67)IMP-1-V67IIMP-10 (F67)IMP-1-V67AIMP-1 (V67)IMP-1-V67IIMP-10 (F67)
Cephalothin500 ± 2050 ± 1470 ± 20450 ± 409.2 ± 0.64.5 ± 0.28.4 ± 0.58 ± 155 ± 211.1 ± 0.255 ± 156 ± 2
Cefotaxime230 ± 1016.4 ± 0.446 ± 2140 ± 1014 ± 15.1 ± 0.85.8 ± 0.511 ± 117 ± 13.2 ± 0.58.0 ± 0.313 ± 1
Ceftazidime8 ± 114 ± 129 ± 666 ± 825 ± 655 ± 750 ± 1049 ± 100.32 ± 0.050.25 ± 0.020.59 ± 0.031.4 ± 0.1
Cefoxitin27 ± 116.2 ± 0.122 ± 122.5 ± 0.54.1 ± 0.44.0 ± 0.16.7 ± 0.53.5 ± 0.56.6 ± 0.54.0 ± 0.13.2 ± 0.16.4 ± 0.6
Benzylpenicillin41 ± 12,000 ± 100860 ± 70110 ± 2098 ± 15530 ± 50350 ± 60300 ± 900.42 ± 0.053.8 ± 0.12.5 ± 0.20.37 ± 0.07
Ampicillin38 ± 2260 ± 30310 ± 30126 ± 1285 ± 9210 ± 30360 ± 60660 ± 800.45 ± 0.021.2 ± 0.10.9 ± 0.10.19 ± 0.01
Imipenem114 ± 5105 ± 5160 ± 20780 ± 9031 ± 335 ± 436 ± 760 ± 103.6 ± 0.13.0 ± 0.24.6 ± 0.413 ± 1
Meropenem390 ± 3022 ± 153 ± 1114 ± 319 ± 22.9 ± 0.22.3 ± 0.16.3 ± 0.221 ± 17.7 ± 0.423 ± 118.2 ± 0.2
Doripenem140 ± 1037 ± 8134 ± 652 ± 121 ± 235 ± 618 ± 26.7 ± 0.77.0 ± 0.21.1 ± 0.17.7 ± 0.67.8 ± 0.6
AztreonamNDNDNDND
  • a Amino acid identities are shown in bold. Data for IMP-1 are from reference 33. ND, not detectable.