title: Thiomandelic acid, a broad spectrum inhibitor of zinc beta-lactamases: kinetic and spectroscopic studies.
abstract: Resistance to beta-lactam antibiotics mediated by metallo-beta-lactamases is an increasingly worrying clinical problem. Candidate inhibitors include mercaptocarboxylic acids, and we report studies of a simple such compound, thiomandelic acid. A series of 35 analogues were synthesized and examined as metallo-beta-lactamase inhibitors. The K(i) values (Bacillus cereus enzyme) are 0.09 microm for R-thiomandelic acid and 1.28 microm for the S-isomer. Structure-activity relationships show that the thiol is essential for activity and the carboxylate increases potency; the affinity is greatest when these groups are close together. Thioesters of thiomandelic acid are substrates for the enzyme, liberating thiomandelic acid, suggesting a starting point for the design of "pro-drugs." Importantly, thiomandelic acid is a broad spectrum inhibitor of metallo-beta-lactamases, with a submicromolar K(i) value for all nine enzymes tested, except the Aeromonas hydrophila enzyme; such a wide spectrum of activity is unprecedented. The binding of thiomandelic acid to the B. cereus enzyme was studied by NMR; the results are consistent with the idea that the inhibitor thiol binds to both zinc ions, while its carboxylate binds to Arg(91). Amide chemical shift perturbations for residues 30-40 (the beta(3)-beta(4) loop) suggest that this small inhibitor induces a movement of this loop of the kind seen for other larger inhibitors.
authors.affiliation: Biological NMR Centre, Department of Biochemistry, University of Leicester, P.O. Box 138, University Rd., Leicester LE1 9HN, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Mollard
authors.forename: C
authors.initials: C
authors.lastname: Moali
authors.forename: C
authors.initials: C
authors.lastname: Papamicael
authors.forename: C
authors.initials: C
authors.lastname: Damblon
authors.forename: S
authors.initials: S
authors.lastname: Vessilier
authors.forename: G
authors.initials: G
authors.lastname: Amicosante
authors.forename: C J
authors.initials: CJ
authors.lastname: Schofield
authors.forename: M
authors.initials: M
authors.lastname: Galleni
authors.forename: J M
authors.initials: JM
authors.lastname: Frere
authors.forename: G C
authors.initials: GC
authors.lastname: Roberts
mesh_terms: D001120:Arginine / Q000737:chemistry; D001665:Binding Sites; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008333:Mandelic Acids / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D008956:Models, Chemical; D008958:Models, Molecular; D011485:Protein Binding; D013053:Spectrophotometry; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D015032:Zinc / Q000737:chemistry / Q000378:metabolism*; D065093:beta-Lactamase Inhibitors
chemical_list: D004791:Enzyme Inhibitors; D008333:Mandelic Acids; D013438:Sulfhydryl Compounds; D065093:beta-Lactamase Inhibitors; C443128:thiomandelic acid; D001120:Arginine; D015032:Zinc