TABLE 2.

Kinetic constants for turnover of β-lactam substrates with the E. cloacae P99 β-lactamase and its Leu-293-Pro mutant derivativea

β-LactamaseKm (μM)kcat (s−1)kcat/Km (M−1 s−1)
LOR
    Wild type68 ± 8826 ± 62(12 ± 1) × 106
    Leu-293-Pro60 ± 6126 ± 9(2.1 ± 0.2) × 106
CAZ
    Wild type15 ± 20.013 ± 0.001(9 ± 1) × 102
    Leu-293-Pro10 ± 30.10 ± 0.01(10 ± 3) × 103
FEP
    Wild type100 ± 160.5 ± 0.1(0.47 ± 0.03) × 104
    Leu-293-Pro24 ± 23.1 ± 0.2(13 ± 1) × 104
  • a Abbreviations: LOR, cephaloridine; CAZ, ceftazidime; FEP, cefepime.