TABLE 2.

Kinetic parameters for purified β-lactamase SHV-38 and purified SHV-1

SubstrateValue fora:
SHV-38SHV-1
kcat (s−1)Km (μM)kcat/Km (mM−1 · s−1)kcat (s−1)Km (μM)kcat/Km (mM−1 · s−1)
Benzylpenicillin100137,7004552023,000
Amoxicillin1,8003551,0009009010,000
Ticarcillin1014b7006022b2,700
Piperacillin100801,3005706010,000
Cephaloridine401502701701101,500
Cephalothin5100501026400
Cefuroxime0.528020.51005
Cefotaxime18001NHNDND
Ceftriaxone601,26050>15>3,000>5
Ceftazidime1103,80030NHNDND
Cefepime31,6002>100>3,000>35
Cefpirome36005>4,000>120>30
Aztreonam35,5000.5NHNDND
Imipenem0.01240.5NHNDND
  • a Values are expressed as the mean of three independent measures (standard deviations were within 15%). NH, not hydrolyzed (the initial rate of hydrolysis was lower than 0.01 μM−1·s−1); ND, not determined due to a Km value that was too high or undetectable hydrolysis.

  • b In the presence of a low Km value, the Ki value was determined with amoxicillin as a competitor.