TABLE 3.
Kinetic parameters of the Acinetobacter genomic species 3 AmpC β-lactamase
| Antibiotic | Km (μM) | Relative Vmax (%)a | Vmax/Km | Relative Vmax/Km (%)a | Hydrolysis rate (μmol/min/μl)b | Relative hydrolysis rate (%)a | IC50 (μM)c |
|---|---|---|---|---|---|---|---|
| Ampicillin | 53 | 100 | 31 | 100 | 420 | 100 | |
| Cephalothin | 100 | 20,000 | 3330 | 10,600 | 28,400 | 6,770 | |
| Cefoxitin | 1 | 6 | 152 | 482 | 111 | 26 | |
| Cefuroxime | 52 | 46 | 15 | 47 | 63 | 15 | |
| Cefotaxime | NDd | ND | ND | ND | 19 | 4 | |
| Imipenem | ND | ND | ND | ND | 9 | 2 | |
| Ceftazidime | ND | ND | ND | ND | <0.1 | NHe | |
| Clavulanic acid | >250 | ||||||
| Sulbactam | 13 |
a
Normalized with respect to value for ampicillin (taken as 100%).
b
Hydrolysis rates were determined by using 100 μM concentrations of the indicated substrates.
c
IC50, 50% inhibitory concentration.
d
ND, not done.
e
NH, no hydrolysis detected.