Kinetic constantsa of PBP 1 and PBP 1* for interaction with β-lactam antibiotics

AntibioticPBP 1PBP 1*
k2/K' (M−1s−1)k3 (s−1)k2/K'(M−1s−1)k3 (s−1)
[125I]IPV1,171 ± 425>10−5293 ± 143>10−5
Penicillin G4,036 ± 1,316>10−51,156 ± 200>10−5
Ceftriaxone20,649 ± 2,476>10−57,048 ± 1,512>10−5
Cephaloradine217 ± 39>10−566 ± 16>10−5
  • a k2/K' values of the purified PBPs for [125I]IPV were derived from the slopes of the apparent rate constant, ka, for formation of the acyl-enzyme complex versus concentration of [125I]IPV, while the k2/K' values for the other antibiotics were obtained from the competition of [125I]IPV binding as described in Materials and Methods. k3 values were obtained either by quantitating the loss of radioactivity from the protein over time ([125I]IPV) or by quantitating the gain of [125I]IPV binding over time (all other antibiotics).