Table 3.

Steady-state kinetic parameters of the purified GES-1 β-lactamasea

Substratekcat (s−1)Km (μM)kcat/Km (mM−1 · s−1)
Benzylpenicillin2.84070
Amoxicillin1320065
Ticarcillin0.34000.7
Piperacillin89009
Cephalothin1793,40052
Cephaloridine532,00026
Cefoxitin0.93033
Ceftazidime3802,000188
Cefepime2.81,8001.6
Cefotaxime684,60015
Imipenem0.003450.07
Aztreonamb
• a Values are means of three independent measures (standard deviations of the values were within 15%).

• b —, not determinable (the initial rate of hydrolysis was lower than 0.001 μM−1 · s−1).