title: Beta-lactamase inhibitors. The inhibition of serine beta-lactamases by specific boronic acids.
abstract: Many beta-lactamases have active-site serine residues, and are competitively inhibited by boronic acids. Hitherto, the boronic acids used have lacked any structural resemblance to the substrates of beta-lactamases. Phenylacetamidomethaneboronic acid, trifluoroacetamidomethaneboronic acid and 2,6-dimethoxybenzamidomethaneboronic acid have now been synthesized. The first of these contains the side-chain moiety of penicillin G, and the last that of methicillin. The pH-dependence of binding of the first inhibitor to beta-lactamase I from Bacillus cereus revealed pK values of 4.7 and 8.2 for (presumably) active-site groups in the enzyme. The kinetics of inhibition were studied by cryoenzymology and by stopped-flow spectrophotometry. These techniques provided evidence for a two-step mechanism of binding of the first two boronic acids mentioned above to beta-lactamase I, and for benzeneboronic acid to a beta-lactamase from Pseudomonas aeruginosa. The slower step is probably associated with a change in enzyme conformation as well as the formation of an O-B bond between the active-site serine hydroxy group and the boronic acid.
mesh_terms: D001409:Bacillus cereus / Q000201:enzymology; D001665:Binding Sites; D001897:Boronic Acids / Q000138:chemical synthesis / Q000494:pharmacology*; D002511:Cephalosporins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000037:antagonists & inhibitors*; D007700:Kinetics; D008956:Models, Chemical; D011485:Protein Binding; D013816:Thermodynamics; D065093:beta-Lactamase Inhibitors
chemical_list: D001897:Boronic Acids; D002511:Cephalosporins; D007527:Isoenzymes; D065093:beta-Lactamase Inhibitors; C021720:nitrocefin