Faraci W S, Pratt R F
Biochem J. 1986 Aug 15;238(1):309-12. doi: 10.1042/bj2380309.
The influence and fate of the 3'-substituent of a series of cephalosporins on their interaction with the DD-transpeptidase/carboxypeptidase of Streptomyces R61 were investigated. Good 3'-leaving groups are eliminated from the acyl-enzyme before deacylation, and hence cephalosporins with such substituents generate a common covalent intermediate. The rate of this elimination reaction in the two cases studied in detail was much lower than from the corresponding cephalosporoates in free solution. Cephalosporins without good 3'-leaving groups yield acyl-enzymes that appear to hydrolyse, leading to enzyme re-activation, faster than those from cephalosporins with leaving groups.
研究了一系列头孢菌素的3'-取代基对其与链霉菌R61的DD-转肽酶/羧肽酶相互作用的影响及命运。在脱酰化之前，良好的3'-离去基团会从酰基酶中消除，因此具有此类取代基的头孢菌素会生成一种常见的共价中间体。在详细研究的两种情况下，这种消除反应的速率远低于游离溶液中相应头孢酸酯的反应速率。没有良好3'-离去基团的头孢菌素产生的酰基酶似乎比有离去基团的头孢菌素产生的酰基酶水解得更快，从而导致酶重新激活。
