Table 4

Kinetic constants for selected Y105 variants and substratesa

SHVNitrocefinAmpicillinCephalothin
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(2.1 ± 0.4) × 10219 ± 211 ± 1(3.1 ± 0.9) × 103(1.8 ± 0.3) × 10117 ± 2(5 ± 1) × 10126 ± 42.0 ± 0.2
Y105E(1.2 ± 0.2) × 102(1.0 ± 0.1) × 1021.2 ± 0.1(1.4 ± 0.7) × 102(1.5 ± 0.6) × 1030.9 ± 0.111 ± 37.2 ± 0.91.5 ± 0.2
Y105F(1.2 ± 0.4) × 10211 ± 211 ± 2(2.4 ± 0.7) × 103(2.4 ± 0.5) × 10210 ± 120 ± 76 ± 23.3 ± 0.8
Y105 M(1.5 ± 0.3) × 10222 ± 36.6 ± 0.6(7 ± 1) × 102(1.2 ± 0.1) × 1025.7 ± 0.412 ± 231 ± 40.37 ± 0.03
Y105R(1.4 ± 0.3) × 10231 ± 44.4 ± 0.4(1.2 ± 0.3) × 103(6 ± 1) × 1022.0 ± 0.2(3 ± 1) × 101(8 ± 2) × 1010.40 ± 0.04
  • a Determinations of kinetic parameters were performed in triplicate, and values are reported as means and standard deviations.