TABLE 2.
Kinetic parameters determined for the cytoplasmic fraction of E. coli LMG-194 producing FLC-1
| Antibiotic | Protein concn (μg · ml)a,b | Km (μM) | Vmax/μg proteinc | Relative kcat/Km |
|---|---|---|---|---|
| Ampicillin | 5.53 | 1,649 ± 174.2 | (1,490 ± 70) × 10−3 | 1.00 |
| Meropenem | 100 | 32.4 ± 9.3 | (2.05 ± 0.14) × 10−3 | 0.07 |
| Imipenem | 17.68 | 177.2 ± 12.5 | (48.61 ± 1.40) × 10−3 | 0.30 |
| Ertapenem | 44.21 | 29.6 ± 11.7 | (6.34 ± 0.67) × 10−3 | 0.24 |
| Cefotaxime | 106.1 | 377.1 ± 110.6 | (7.85 ± 1.25) × 10−3 | 0.02 |
| Ceftazidime | NDd | <65 × 10−3e | ||
| Cefepime | NDd | <34 × 10−3e |
a
Protein concentration of the cytoplasmic fraction.
b
The E. coli strain producing FLC and the nontransformed strain were used to prepare cytoplasmic fractions. The highest tested concentration of both preparations was 176.83 μg/ml. None of the tested antibiotics were hydrolyzed by the nontransformed E. coli cytoplasmic fraction.
c
Expressed as μM/s/μg of protein.
d
Not determinable.
e
Because no substrate hydrolysis was detected, the Vmax data for ceftazidime and cefepime have been reported as less than the limit of detection/μg protein.