TABLE 1.
Steady-state kinetics of hydrolysis for ceftiofur, DFC, DFC-cysteine, DFC-dimer, and ampicillin by recombinant CMY-2, CTX-M-15, and KPC-3a
| Substrate | β-Lactamase | Vmax (μmol/s) | Km (μM) | Kcat (s−1) | Kcat/Km (μM−1 s−1) |
|---|---|---|---|---|---|
| Ceftiofur | CMY-2 | 1.31 ± 0.03 | 994.1 ± 34.8 | 131.3 ± 9.4 | 0.132 ± 0.01 |
| CTX-M-15b | 3.14 ± 0.07 | 330.0 ± 14.1 | 313.7 ± 13.0 | 0.95 ± 0.09 | |
| KPC-3 | 1.92 ± 0.07 | 249.3 ± 20.7 | 192.6 ± 6.1 | 0.77 ± 0.029 | |
| DFC | CMY-2 | 1.80 ± 0.1 | 134.9 ± 7.8 | 180.0 ± 5.4 | 1.33 ± 0.06 |
| CTX-M-15b | 4.89 ± 0.2 | 141.2 ± 11.2 | 489.8 ± 16.2 | 3.46 ± 0.14 | |
| KPC-3 | 2.40 ± 0.03 | 107.1 ± 9.0 | 240.7 ± 8.2 | 2.24 ± 0.09 | |
| DFC-cysteine | CMY-2 | 0.124 ± 0.0 | 44.49 ± 2.0 | 12.4 ± 0.1 | 0.28 ± 0.05 |
| CTX-M-15 | 0.58 ± 0.03 | 111.2 ± 5.9 | 58.66 ± 4.5 | 0.527 ± 0.007 | |
| KPC-3 | 0.114 ± 0.01 | 260.5 ± 7.4 | 11.43 ± 0.7 | 0.043 ± 0.001 | |
| DFC-dimer | CMY-2 | 1.04 ± 0.0 | 116.8 ± 6.4 | 104.1 ± 9.0 | 0.891 ± 0.014 |
| CTX-M-15 | 1.17 ± 0.0 | 227.8 ± 11.6 | 117.2 ± 7.6 | 0.51 ± 0.006 | |
| KPC-3 | 0.454 ± 0.0 | 933.6 ± 55.2 | 45.42 ± 0.2 | 0.048 ± 0.003 | |
| Ampicillin | CMY-2 | 0.48 ± 0.01 | 387.4 ± 1.9 | 48.84 ± 2.3 | 0.126 ± 0.012 |
| CTX-M-15b | 1.01 ± 0.06 | 197.8 ± 13.0 | 101.9 ± 5.6 | 0.515 ± 0.004 | |
| KPC-3 | 0.72 ± 0.0 | 286.1 ± 13.8 | 72.36 ± 24.3 | 0.253 ± 0.017 |
a
All values are the averages of three independent replicates ± SEM.
b
Parameter estimates for CTX-M-15 were published by Ahmadvand et al. (48).