PT - JOURNAL ARTICLE AU - Bush, K AU - Macalintal, C AU - Rasmussen, B A AU - Lee, V J AU - Yang, Y TI - Kinetic interactions of tazobactam with beta-lactamases from all major structural classes. AID - 10.1128/AAC.37.4.851 DP - 1993 Apr 01 TA - Antimicrobial Agents and Chemotherapy PG - 851--858 VI - 37 IP - 4 4099 - http://aac.asm.org/content/37/4/851.short 4100 - http://aac.asm.org/content/37/4/851.full SO - Antimicrob. Agents Chemother.1993 Apr 01; 37 AB - 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.