Table 4.

Kinetic parameters for OXA-17 β-lactamase compared with OXA-10

SubstrateOXA-17 (linear kinetics)OXA-10a
Km (μM)kcat(s−1)kcat/Km b VssVo
Km (s−1)kcat(s−1)kcat/Km b Km (μM)kcat(s−1)kcat/Km b
Penicillin G34 ± 0.6c 5 ± 0.114763 ± 689 ± 101,412d
Ampicillin245 ± 3726 ± 0.2106235 ± 30587 ± 302,50077 ± 9531 ± 126,896
Carbenicillin296 ± 312 ± 0.421195 ± 1331 ± 1159370 ± 44126 ± 5340
Oxacillin153 ± 13120 ± 2.0784222 ± 16608 ± 10273996 ± 8660 ± 106,870
Cloxacillin573 ± 7920 ± 1.0352,640 ± 323520 ± 361961,110 ± 1002,682 ± 1502,416
Cephaloridine2,940 ± 18223 ± 1.082,340 ± 30079 ± 833395 ± 8339 ± 398
Cephalothin286 ± 605 ± 0.11738 ± 26 ± 0.1158
Cefotaxime2,240 ± 42722 ± 3.010346 ± 199 ± 0.226
Ceftriaxone544 ± 521 ± 0.05255 ± 23 ± 0.354
CeftazidimeNDe NDNDNDND
  • a OXA-10 β-lactamase was shown previously (8) to give biphasic kinetics, so two sets of kinetics parameters could be determined for the initial (Vo ) and steady-state (Vss ) phases of hydrolysis.

  • b (k cat/Km ) × 1,000 in micromolar−1 second−1.

  • c Values are means ± standard error.

  • d −, results not available.

  • e ND, hydrolysis not detected.