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.