TABLE 2.
Kinetic parameters and relative kcat/Km values of purified β-lactamase OXA-55 from S. algae KB-1, OXA-54 from S. oneidensis MR-1, and OXA-40 from A. baumannii CLA-1a
| Substrate | OXA-55
|
OXA-54 (relative kcat/Km)b | OXA-40 (relative kcat/Km)c | |||
|---|---|---|---|---|---|---|
| kcat (s−1) | Km (μM) | kcat/Km (mM−1 · s−1) | Relative kcat/Km | |||
| Benzylpenicillin | 4 | 25 | 160 | 100 | 100 | 100 |
| Ampicillin | 8 | 500 | 15 | 10 | 6 | 9 |
| Ticarcillin | 1 | 20 | 50 | 31 | 6 | 9 |
| Piperacillin | 3 | 110 | 30 | 17 | 4 | 23 |
| Cephalothin | 0.6 | 70 | 10 | 5 | 0.5 | 23 |
| Cephaloridine | 10 | 750 | 15 | 9 | 1.5 | 2 |
| Cefotaxime | ND | — | — | — | 0.4 | — |
| Ceftazidime | 2 | 4,700 | 0.5 | 0.25 | — | 5 |
| Cefepime | ND | — | — | — | 0.1 | — |
| Cefpirome | 0.1 | 670 | 0.1 | 0.06 | 2 | — |
| Oxacillin | 5 | 390 | 10 | 6 | 23 | 1 |
| Cloxacillin | 0.5 | 190 | 3 | 1.5 | — | — |
| Aztreonam | ND | — | — | — | — | — |
| Imipenem | 0.1 | 20 | 5 | 3 | 10 | 7 |
| Meropenem | 0.05 | 500 | 0.1 | 0.06 | 0.02 | — |
a
Data are means of three independent experiments. Standard deviations were within 10% of the means. Relative values were calculated according to the value obtained for benzylpenicillin, which was set at 100. ND, no detectable hydrolysis (< 0.01 s−1). —, not determinable.
b
Data are from reference 19.
c
Data are from reference 11.