TABLE 2.
Kinetic parameters of the purified IMP-2 enzyme
| Substrate | Km (μM)ab | kcat (s−1)a | kcat/Km (μM−1 s−1) |
|---|---|---|---|
| Ampicillin | 110 ± 10 (200)c | 23 ± 2 (950) | 0.21 (4.8) |
| Carbenicillin | 700 ± 65 (NAd) | 252 ± 20 (NA) | 0.36 (0.02) |
| Nitrocefin | 95 ± 7 (27) | 275 ± 22 (63) | 2.9 (2.3) |
| Cephaloridine | 3 ± 0.2 (22) | 0.8 ± 0.06 (53) | 0.27 (2.4) |
| Cefoxitin | 7 ± 0.5 (8) | 7 ± 0.7 (16) | 1.0 (2.0) |
| Ceftazidime | 111 ± 9 (44) | 21 ± 2 (8) | 0.19 (0.18) |
| Cefepime | 7 ± 0.6 (11) | 4 ± 0.2 (7) | 0.57 (0.66) |
| Imipenem | 24 ± 2 (39) | 22 ± 2 (46) | 0.92 (1.2) |
| Meropenem | 0.3 ± 0.03 (10) | 1 ± 0.08 (5) | 3.3 (0.5) |
| Aztreonam | NDe | NHf | ND |
a
Values are means ± standard deviations of three measurements.
b
Determined as Ki when Km was lower than 10 μM.
c
Data in parentheses report the corresponding values previously measured for the IMP-1 enzyme (21).
d
NA, not available.
e
ND, not determined.
f
NH, no hydrolysis detected.