Mobashery S, Johnston M
J Biol Chem. 1986 Jun 15;261(17):7879-87.
Two novel C10-(dipeptidyl)cephalosporin esters (3-(beta-chloro-L-alanyl-beta-chloro-L-alanyloxymethyl)-7 beta-(2-thienylacetamido)-3-cephem-4-carboxylic acid (7) and sodium 3-(L-alanyl-L-alanyloxymethyl)-7 beta-(2-thienylacetamido)-3-cephem-4-carboxylate, toluene-sulfonic acid salt (18] were synthesized, and their reactions with Escherichia coli TEM beta-lactamase were examined. Kinetic parameters determined for the enzymatic reactions of 7 (Km = 0.32 mM; Vmax = 338 mumol min-1 (mg protein)-1) and of 18 (Km = 0.33 mM, Vmax = 338 mumol min-1 (mg protein)-1) demonstrate that both of the peptidyl esters are good substrates for the lactamase. In fact, the Vmax rates for 7 and 18 are each more than 4-fold greater than that obtained for cephalothin, 1 (Vmax = 78 mumol min-1 (mg protein)-1), a well characterized substrate for the lactamases. Analysis of the enzymatic reactions by high field (500 MHz) 1H NMR revealed similar patterns for fragmentation of the cephem nucleus of 1, 7, and 18. However, while hydrolysis of 1 produces acetate, cleavage of 7 and 18 releases beta Cl-LAla-beta Cl-LAla and LAla-LAla, respectively, from the dipeptidyl cephalosporin esters. Based on these findings, a strategy for co-opting the beta-lactamases of Gram-negative bacteria for "delivery" of bactericidal agents is described, and an explanation for the previously reported (Mobashery, S., Lerner, S.A., and Johnston, M. (1986) J. Am. Chem. Soc. 108, 1685) antibacterial activity of 7 is offered.
合成了两种新型的C10 -（二肽基）头孢菌素酯（3 -（β - 氯 - L - 丙氨酰 - β - 氯 - L - 丙氨酰氧基甲基）-7β -（2 - 噻吩乙酰氨基）-3 - 头孢烯 - 4 - 羧酸（7）和3 -（L - 丙氨酰 - L - 丙氨酰氧基甲基）-7β -（2 - 噻吩乙酰氨基）-3 - 头孢烯 - 4 - 羧酸钠甲苯磺酸盐（18），并检测了它们与大肠杆菌TEMβ - 内酰胺酶的反应。测定了7（Km = 0.32 mM；Vmax = 338 μmol min-1（mg蛋白质）-1）和18（Km = 0.33 mM，Vmax = 338 μmol min-1（mg蛋白质）-1）酶促反应的动力学参数，结果表明这两种肽基酯都是β - 内酰胺酶的良好底物。事实上，7和18的Vmax速率均比头孢噻吩（1，Vmax = 78 μmol min-1（mg蛋白质）-1）高4倍多，头孢噻吩是一种已被充分表征的β - 内酰胺酶底物。通过高场（500 MHz）1H NMR对酶促反应进行分析，发现1、7和18的头孢烯核裂解模式相似。然而，虽然1水解产生乙酸盐，但7和18的裂解分别从二肽基头孢菌素酯中释放出β - Cl - LAla - β - Cl - LAla和LAla - LAla。基于这些发现，描述了一种利用革兰氏阴性菌的β - 内酰胺酶进行杀菌剂“递送”的策略，并对先前报道的（莫巴舍里，S.，勒纳，S.A.，和约翰斯顿，M.（1986）J. Am. Chem. Soc. 108，1685）7的抗菌活性提供了解释。
