TABLE 3.
Steady-state kinetic parameters for PenA and PenI with selected β-lactams
Km and kcat values were determined under pseudo-first order conditions, and a nonlinear least square fit of the data to the Henri-Michaelis-Menten equation was determined using the kinetic parameters. Each experiment was completed in triplicate, and the error values represent the mean ± S.E.
| Km | kcat | kcat/Km | |
|---|---|---|---|
| μm | s−1 | μm−1 s−1 | |
| AMP | |||
| PenA | 88 ± 9 | 285 ± 29 | 3.2 ± 0.3 |
| PenI | 12 ± 3 | 0.69 ± 0.07 | 0.06 ± 0.01 |
| THIN | |||
| PenA | 71 ± 7 | 221 ± 21 | 3.1 ± 0.3 |
| PenI | 42 ± 4 | 4.2 ± 0.4 | 0.10 ± 0.01 |
| TAX | |||
| PenA | 295 ± 30 | 142 ± 14 | 0.48 ± 0.05 |
| PenI | 410 ± 41 | 9.0 ± 0.9 | 0.022 ± 0.002 |
| Nitrocefin | |||
| PenA | 142 ± 14 | 460 ± 46 | 3.2 ± 0.3 |
| PenI | 35 ± 4 | 4.9 ± 0.4 | 0.14 ± 0.01 |
| AZT | |||
| PenA | 378 ± 40 | 60 ± 6 | 0.16 ± 0.02 |
| PenI | 104 ± 10 | 2.1 ± 0.2 | 0.020 ± 0.002 |
| IMI | |||
| PenA | 7 ± 1 | 0.38 ± 0.04 | 0.05 ± 0.01 |
| PenI | NDa | ND | ND |
a ND means no measurable hydrolysis of imipenem was detected.