title: Evaluation of inhibition of the carbenicillin-hydrolyzing beta-lactamase PSE-4 by the clinically used mechanism-based inhibitors.
abstract: Characterization of the biochemical steps in the inactivation chemistry of clavulanic acid, sulbactam and tazobactam with the carbenicillin-hydrolyzing beta-lactamase PSE-4 from Pseudomonas aeruginosa is described. Although tazobactam showed the highest affinity to the enzyme, all three inactivators were excellent inhibitors for this enzyme. Transient inhibition was observed for the three inactivators before the onset of irreversible inactivation of the enzyme. Partition ratios (k(cat)/k(inact)) of 11, 41 and 131 were obtained with clavulanic acid, tazobactam and sulbactam, respectively. Furthermore, these values were found to be 14-fold, 3-fold and 80-fold lower, respectively, than the values obtained for the clinically important TEM-1 beta-lactamase. The kinetic findings were put in perspective by determining the computational models for the pre-acylation complexes and the immediate acyl-enzyme intermediates for all three inactivators. A discussion of the pertinent structural factors is presented, with PSE-4 showing subtle differences in interactions with the three inhibitors compared to the TEM-1 enzyme.
authors.affiliation: Microbiologie moléculaire et génie des protéines, Sciences de la vie et de la santé, Faculté de médecine, pavillon Charles-Eugène-Marchand, Université Laval, Ste-Foy, Que., Canada.
authors.forename: C
authors.initials: C
authors.lastname: Therrien
authors.forename: L P
authors.initials: LP
authors.lastname: Kotra
authors.forename: F
authors.initials: F
authors.lastname: Sanschagrin
authors.forename: S
authors.initials: S
authors.lastname: Mobashery
authors.forename: R C
authors.initials: RC
authors.lastname: Levesque
mesh_terms: D000215:Acylation / Q000187:drug effects; D001665:Binding Sites; D002228:Carbenicillin / Q000378:metabolism*; D019818:Clavulanic Acid / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D003198:Computer Simulation; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D004926:Escherichia coli / Q000201:enzymology; D006860:Hydrogen Bonding; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D008968:Molecular Conformation; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010403:Penicillin Resistance; D010405:Penicillinase / Q000737:chemistry / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000201:enzymology*; D013407:Sulbactam / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000078142:Tazobactam; D013816:Thermodynamics; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D065093:beta-Lactamase Inhibitors; D019818:Clavulanic Acid; D010397:Penicillanic Acid; D010405:Penicillinase; D001618:beta-Lactamases; C034413:beta-lactamase TEM-1; D002228:Carbenicillin; D013407:Sulbactam; D000078142:Tazobactam