TABLE 5.

Kinetic parameters of purified PenB1 β-lactamasea

Substratekcat (s−1)Km (μM)kcat/Km (mM−1 · s−1)
Benzylpenicillin130255,200
Ampicillin70100700
Ticarcillin1560250
Piperacillin510500
Cephalothin3001003,000
Cefuroxime170802,100
CefoxitinNDbNDND
Cefotaxime20150130
Ceftazidime1.53,0000.5
Cefepime101,00010
Aztreonam302,50010
Imipenem0.1602
Meropenem12,5000.5
  • a The data are the means of three independent experiments. Standard deviations were within 10% of the means.

  • b ND, no detectable hydrolysis (<0.01 s−1) with a maximum amount of 5 μg of purified enzyme and up to 200 nmol of substrate.