TABLE 2.
Kinetic constants of the four enzymes studied against 10 β-lactam antibacterialsa
| β-Lactam |
kcat (s−1) |
Km (μM) |
kcat/Km (μM−1 s−1) |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| IMP-1-V67A | IMP-1 (V67) | IMP-1-V67I | IMP-10 (F67) | IMP-1-V67A | IMP-1 (V67) | IMP-1-V67I | IMP-10 (F67) | IMP-1-V67A | IMP-1 (V67) | IMP-1-V67I | IMP-10 (F67) | |
| Cephalothin | 500 ± 20 | 50 ± 1 | 470 ± 20 | 450 ± 40 | 9.2 ± 0.6 | 4.5 ± 0.2 | 8.4 ± 0.5 | 8 ± 1 | 55 ± 2 | 11.1 ± 0.2 | 55 ± 1 | 56 ± 2 |
| Cefotaxime | 230 ± 10 | 16.4 ± 0.4 | 46 ± 2 | 140 ± 10 | 14 ± 1 | 5.1 ± 0.8 | 5.8 ± 0.5 | 11 ± 1 | 17 ± 1 | 3.2 ± 0.5 | 8.0 ± 0.3 | 13 ± 1 |
| Ceftazidime | 8 ± 1 | 14 ± 1 | 29 ± 6 | 66 ± 8 | 25 ± 6 | 55 ± 7 | 50 ± 10 | 49 ± 10 | 0.32 ± 0.05 | 0.25 ± 0.02 | 0.59 ± 0.03 | 1.4 ± 0.1 |
| Cefoxitin | 27 ± 1 | 16.2 ± 0.1 | 22 ± 1 | 22.5 ± 0.5 | 4.1 ± 0.4 | 4.0 ± 0.1 | 6.7 ± 0.5 | 3.5 ± 0.5 | 6.6 ± 0.5 | 4.0 ± 0.1 | 3.2 ± 0.1 | 6.4 ± 0.6 |
| Benzylpenicillin | 41 ± 1 | 2,000 ± 100 | 860 ± 70 | 110 ± 20 | 98 ± 15 | 530 ± 50 | 350 ± 60 | 300 ± 90 | 0.42 ± 0.05 | 3.8 ± 0.1 | 2.5 ± 0.2 | 0.37 ± 0.07 |
| Ampicillin | 38 ± 2 | 260 ± 30 | 310 ± 30 | 126 ± 12 | 85 ± 9 | 210 ± 30 | 360 ± 60 | 660 ± 80 | 0.45 ± 0.02 | 1.2 ± 0.1 | 0.9 ± 0.1 | 0.19 ± 0.01 |
| Imipenem | 114 ± 5 | 105 ± 5 | 160 ± 20 | 780 ± 90 | 31 ± 3 | 35 ± 4 | 36 ± 7 | 60 ± 10 | 3.6 ± 0.1 | 3.0 ± 0.2 | 4.6 ± 0.4 | 13 ± 1 |
| Meropenem | 390 ± 30 | 22 ± 1 | 53 ± 1 | 114 ± 3 | 19 ± 2 | 2.9 ± 0.2 | 2.3 ± 0.1 | 6.3 ± 0.2 | 21 ± 1 | 7.7 ± 0.4 | 23 ± 1 | 18.2 ± 0.2 |
| Doripenem | 140 ± 10 | 37 ± 8 | 134 ± 6 | 52 ± 1 | 21 ± 2 | 35 ± 6 | 18 ± 2 | 6.7 ± 0.7 | 7.0 ± 0.2 | 1.1 ± 0.1 | 7.7 ± 0.6 | 7.8 ± 0.6 |
| Aztreonam | ND | ND | ND | ND | ||||||||
a
Amino acid identities are shown in bold. Data for IMP-1 are from reference 33. ND, not detectable.