TABLE 4.

Substrate and inhibitor profile of the ADC-7 β-lactamase

β-LactamKm (or Ki)a (μM), correctedVmax (μM s−1)kcat (s−1)kcat/Km (μM−1 s−1)
Nitrocefin53 ± 82.1 ± 0.11,750 ± 8333 ± 3
Cephaloridine45 ± 171.43 ± 0.21,189 ± 16626 ± 6
Cephalothin40 ± 111.5 ± 0.11,154 ± 8029 ± 6
Cefoxitin0.34 ± 0.090.09 ± 0.010.92 ± 0.032.7 ± 0.6
Cefepime(594 ± 6)NM
Aztreonam(0.7 ± 0.1)NM
Ceftazidime(11.6 ± 1.6)NM
Cefotaxime(0.10 ± 0.02)NM
Tazobactam(91 ± 21)
Sulbactam(109 ± 3)
Clavulanic acid(4,275 ± 253)
Imipenem(2.0 ± 0.3)
Sulopenem(10.7 ± 2.0)
Meropenem(38 ± 4)
Ertapenem(3.8 ± 0.3)
  • a The affinity of each of these substrates for the ADC-7 β-lactamase (“true Ki”) was determined by performing a competition reaction using nitrocefin as the indicator substrate. NM, not measurable using 100 nM ADC-7 β-lactamase.