Bush K, Macalintal C, Rasmussen B A, Lee V J, Yang Y
Medical Research Division, American Cyanamid, Pearl River, New York 10965.
Antimicrob Agents Chemother. 1993 Apr;37(4):851-8. doi: 10.1128/AAC.37.4.851.
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.
他唑巴坦被证明是1、2a、2b和2b'组β-内酰胺酶的有效抑制剂。对A类和C类丝氨酸β-内酰胺酶进行的扩展动力学研究表明，PC1、TEM-2和P99酶在失活之前均被可逆抑制。CcrA金属β-内酰胺酶的抑制效果较差，其50%抑制浓度比大多数丝氨酸β-内酰胺酶的50%抑制浓度至少低3个数量级。PC1、TEM-2、P99和CcrA酶失活前他唑巴坦的水解周转数分别为2、125、50和4000。在光谱研究中，他唑巴坦与PC1、TEM-2和CcrAβ-内酰胺酶反应后形成了瞬态中间体，这与负责他唑巴坦水解的酶相关中间体相对应。观察到这些反应中间体在270nm（CcrA）和288nm（TEM-2和PC1）处有发色团吸收。P99头孢菌素酶形成了一种在295nm处有最大紫外吸收的稳定复合物。他唑巴坦与所有这些酶一起孵育导致了一种具有短波长吸收的他唑巴坦反应产物的积累。该产物具有与他唑巴坦主要真核代谢产物相似的特征。文中提出了可能的反应机制来解释这些发现。总之，在初始的瞬态抑制阶段之后，丝氨酸类和金属β-内酰胺酶均被他唑巴坦不可逆地失活。
