title: Nanomolar inhibitors of AmpC beta-lactamase.
abstract: beta-lactamases are the most widespread resistance mechanism to beta-lactam antibiotics, such as the penicillins and the cephalosporins. In an effort to combat these enzymes, a combination of stereoselective organic synthesis, enzymology, microbiology, and X-ray crystallography was used to design and evaluate new carboxyphenyl-glycylboronic acid transition-state analogue inhibitors of the class C beta-lactamase AmpC. The new compounds improve inhibition by over 2 orders of magnitude compared to analogous glycylboronic acids, with K(i) values as low as 1 nM. On the basis of the differential binding of different analogues, the introduced carboxylate alone contributes about 2.1 kcal/mol in affinity. This carboxylate corresponds to the ubiquitous C3(4)' carboxylate of beta-lactams, and this energy represents the first thermodynamic measurement of the importance of this group in molecular recognition by class C beta-lactamases. The structures of AmpC in complex with two of these inhibitors were determined by X-ray crystallography at 1.72 and 1.83 A resolution. These structures suggest a structural basis for the high affinity of the new compounds and provide templates for further design. The highest affinity inhibitor was 5 orders of magnitude more selective for AmpC than for characteristic serine proteases, such as chymotrypsin. This inhibitor reversed the resistance of clinical pathogens to the third generation cephalosporin ceftazidime; it may serve as a lead compound for drug discovery to combat bacterial resistance to beta-lactam antibiotics.
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, Mission Bay Genentech Hall, 600 16th Street, Mail Box 2240, 94143, USA.
authors.forename: Federica
authors.initials: F
authors.lastname: Morandi
authors.forename: Emilia
authors.initials: E
authors.lastname: Caselli
authors.forename: Stefania
authors.initials: S
authors.lastname: Morandi
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Focia
authors.forename: Jesús
authors.initials: J
authors.lastname: Blázquez
authors.forename: Brian K
authors.initials: BK
authors.lastname: Shoichet
authors.forename: Fabio
authors.initials: F
authors.lastname: Prati
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins; D001896:Boron Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001897:Boronic Acids / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D002442:Ceftazidime / Q000494:pharmacology; D018360:Crystallography, X-Ray; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D008956:Models, Chemical; D008968:Molecular Conformation; D013379:Substrate Specificity; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001896:Boron Compounds; D001897:Boronic Acids; D004791:Enzyme Inhibitors; D065093:beta-Lactamase Inhibitors; C116999:methaneboronic acid; D002442:Ceftazidime; C048795:AmpC beta-lactamases; D001618:beta-Lactamases