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A disulfide bridge near the active site of carbapenem‐hydrolyzing class A β‐lactamases might explain their unusual substrate profile
Author(s) -
Raquet Xavier,
LamotteBrasseur Josette,
Bouillenne Fabrice,
Frère JeanMarie
Publication year - 1997
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/(sici)1097-0134(199701)27:1<47::aid-prot6>3.0.co;2-k
Subject(s) - disulfide bond , substrate (aquarium) , bridge (graph theory) , carbapenem , active site , class (philosophy) , chemistry , combinatorial chemistry , stereochemistry , computer science , biology , enzyme , biochemistry , antibiotics , ecology , artificial intelligence , anatomy
Bacterial resistance to β‐lactam antibiotics, a clinically worrying and recurrent problem, is often due to the production of β‐lactamases, enzymes that efficiently hydrolyze the amide bond of the β‐lactam nucleus. Imipenem and other carbapenems escape the activity of most active site serine β‐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 β‐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 β‐lactamases. In turn, this will contribute to the design of better antibacterial drugs. Three‐dimensional 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 β‐lactamase. The peculiar substrate profile of the carbapenemases appears to be strongly correlated with the presence of the disulfide bridge between C69 and C238. Proteins 27:47–58 © 1997 Wiley‐Liss, Inc.