A disulfide bridge near the active site of carbapenem-hydrolyzing class A β-lactamases might explain their unusual substrate profile
✍ Scribed by Xavier Raquet; Josette Lamotte-Brasseur; Fabrice Bouillenne; Jean-Marie Frère
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 306 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0887-3585
No coin nor oath required. For personal study only.
✦ Synopsis
Bacterial resistance to -lactam antibiotics, a clinically worrying and recurrent problem, is often due to the production of -lactamases, enzymes that efficiently hydrolyze the amide bond of the -lactam nucleus. Imipenem and other carbapenems escape the activity of most active site serine -lactamases and have therefore become very popular drugs for antibacterial chemotherapy in the hospital environment. Their usefulness is, however, threatened by the appearance of new -lactamases that efficiently hydrolyze them. This study is focused on the structure and properties of two recently described class A carbapenemases, produced by Serratia marcescens and Enterobacter cloacae strains and leads to a better understanding of the specificity of -lactamases. In turn, this will contribute to the design of better antibacterial drugs. Threedimensional models of the two class A carbapenemases were constructed by homology modeling. They suggested the presence, near the active site of the enzymes, of a disulfide bridge (C69-C238) whose existence was experimentally confirmed. Kinetic parameters were measured with the purified Sme-1 carbapenemase, and an attempt was made to explain its specific substrate profile by analyzing the structures of minimized Henri-Michaelis complexes and comparing them to those obtained for the ''classical'' TEM-1 -lactamase. The peculiar substrate profile of the carbapenemases appears to be strongly correlated with the presence of the disulfide bridge between C69 and C238.