Kinetic interactions of tazobactam with beta-lactamases from all major structural classes

Antimicrob Agents Chemother. 1993 Apr;37(4):851-8. doi: 10.1128/AAC.37.4.851.

Abstract

Tazobactam was shown to be a potent inhibitor of group 1, 2a, 2b, and 2b' beta-lactamases. Extended kinetic studies with class A and C serine beta-lactamases showed that the PC1, TEM-2, and P99 enzymes all were reversibly inhibited prior to inactivation of the enzymes. The CcrA metallo-beta-lactamase was less well inhibited, with a 50% inhibitory concentration at least 3 orders of magnitude less favorable than those for most serine beta-lactamases. The numbers of hydrolytic turnovers of tazobactam before inactivation were 2 for PC1, 125 for TEM-2, 50 for P99, and 4,000 for the CcrA enzyme. In spectral studies, transient intermediates were formed after reaction of tazobactam with the PC1, TEM-2, and CcrA beta-lactamases, corresponding to enzyme-associated intermediates responsible for hydrolysis of tazobactam. Chromophores absorbing at 270 nm (CcrA) and 288 nm (TEM-2 and PC1) were observed for these reaction intermediates. The P99 cephalosporinase formed a stable complex with a UV maximum at 295 nm. Incubation of tazobactam with all of the enzymes resulted in accumulation of a tazobactam reaction product with a short-wavelength absorbance. This product has characteristics similar to those of the major eucaryotic metabolite of tazobactam. Possible reaction mechanisms are presented to explain the findings. In conclusion, both serine-based and metallo-beta-lactamases were irreversibly inactivated by tazobactam following an initial transient inhibition phase.

MeSH terms

  • Bacterial Proteins / metabolism
  • Cephalosporins / pharmacology
  • Clavulanic Acid
  • Clavulanic Acids / pharmacology
  • Hydrolysis
  • Isoelectric Focusing
  • Kinetics
  • Molecular Weight
  • Penicillanic Acid / metabolism
  • Penicillanic Acid / pharmacology*
  • Spectrophotometry, Ultraviolet
  • Tazobactam
  • beta-Lactamase Inhibitors*
  • beta-Lactamases / analysis
  • beta-Lactamases / isolation & purification

Substances

  • Bacterial Proteins
  • Cephalosporins
  • Clavulanic Acids
  • beta-Lactamase Inhibitors
  • Clavulanic Acid
  • Penicillanic Acid
  • beta-Lactamases
  • beta-lactamase TEM-2
  • carbapenemase
  • nitrocefin
  • Tazobactam