Table 2.

Kinetics parameters of TEM-89 β-lactamase compared with those of TEM-2, TEM-3, and TEM-59 β-lactamases:a

SubstrateTEM-2TEM-3TEM-89TEM-59
kcat(s−1)Km(μM)kcat/Km(μM−1 s−1)kcat(s−1)Km(μM−1)kcat/Km(μM−1 s−1)kcat(s−1)Km(μM−1)kcat/Km(μM−1 s−1)kcat(s−1)Km(μM−1)kcat/Km(μM−1 s−1)
Benzylpenicillin1,50018834567.5508.06.252001401.4
Amoxicillin1,20020603156.250281.791105200.2
Ticarcillin1951216.2924.56240.254NDb<0.01
Piperacillin1,2754031.87212655560.893601203.0
Cephalothin3003500.8648232.15790.06<1ND<0.01
Cephaloridine8258001.043301.451600.03<1ND<0.01
Cefuroxime31,000<0.0128900.31<1ND<0.01<1ND<0.01
Ceftriaxone<1ND<0.0181801<1ND<0.01<1ND<0.01
Cefotaxime1.5ND<0.012021002<1ND<0.01<1ND<0.01
Ceftazidime<1ND<0.01182000.1<1ND<0.01<1ND<0.01
  • a The values given forkcat and Km were computed on the basis of at least three independent experiments. Standard deviations for kcat were 10% for values higher than 100 s−1; otherwise, they were 20%. Standard deviations for Km were 15% for values between 10 and 100 μM, 30% for values higher than 100 μM, and close to 50% for values lower than 10 μM.

  • b ND, not detected (highKm or Ki values).