Table 2.

SubstrateGES-2GES-1
kcat(s−1)Km (μM)kcat/Km (mM−1 · s−1)kcat(s−1)Km (μM)kcat/Km (mM−1 · s−1)
Benzylpenicillin0.44962.84070
Amoxicillin0.725.8261320065
Ticarcillin0.0613.34.50.34000.7
Piperacillin0.322.823890013
Cephalothin0.331121793,40052
Cephaloridine0.57.765532,00026
Cefoxitinb 0.93033
CeftazidimeNDc >3,000ND3802,000188
Cefepime1.11,9000.62.81,8001.6
Cefotaxime2.28902.5684,60015
Imipenem0.0040.4590.003450.07
Meropenem
Aztreonam
• a Parameters of GES-2 are compared to those of GES-1 β-lactamase, as previously published (28). Values are expressed as the mean of three independent measures (standard deviations of the values were within 15%).

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

• c ND, not determinable due to very highKm values.