6-beta-bromopenicillanic acid, a potent beta-lactamase inhibitor.

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Abstract
6-.beta.-Bromopenicillanic acid, which arises from the epimerization of 6-.alpha.-bromopenicillanic acid in aqueous solution or from hydrogenation of 6,6-dibromopenicillanic acid, is a powerful, irreversible, active-site-directed inhibitor of several typical .beta.-lactamases (penicillinase; penicillin amido-.beta.-lactamhydrolase, EC 3.5.2.6); 6-.alpha.-bromopenicillanic acid is inert in all cases. The .beta.-lactamase I of Bacillus cereus is extremely susceptible to inhibition by 6-.beta.-bromopenicillanic acid, being completely inhibited at less than micromolar concentrations through what is probably a 1:1 interaction. The B. licheniformis exoenzyme is similarly susceptible, while the Staphylococcus aureus enzyme and the Escherichia coli (R factor) enzyme are less so; the B. cereus .beta.-lactamase II is not inhibited. Very high concentrations (.gtoreq. 0.1 M) of benzylpenicillin, a good substrate, are required to significantly reduce the rate of inhibition of B. cereus .beta.-lactamase I by 6-.beta.-bromopenicillanic acid.