Table 2

Kinetic constants for selected N152 variants and substratesa

β-LactamaseNitrocefinCefoxitinCefoperazone
kcat (s−1)Km (μM)kcat/Km (s−1 μM−1)kcat (s−1)Km (μM)kcat/Km (s−1 μM−1)kcat (s−1)Km (μM)kcat/Km (s−1 μM−1)
WT CMY-2(4 ± 1) × 10232 ± 812 ± 235 ± 814 ± 22.5 ± 0.240 ± 1010 ± 23.9 ± 0.5
N152G(4 ± 1) × 10290 ± 203.9 ± 0.440 ± 2016 ± 42.3 ± 0.439 ± 711 ± 23.5 ± 0.5
N152S(3.2 ± 0.6) × 10246 ± 56.9 ± 0.553 ± 76.0 ± 0.48.9 ± 540 ± 105 ± 17 ± 1
N152T(4 ± 1) × 102120 ± 203.2 ± 0.640 ± 2013 ± 33.2 ± 0.630 ± 108 ± 24.2 ± 0.6
  • a Determinations of kinetic parameters were performed in triplicate, and values are reported as means ± standard deviations.