title: Irreversible inactivation of beta-lactamase I from Bacillus cereus by chlorinated 6-spiroepoxypenicillins.
abstract: On incubation of the chlorinated 6-spiroepoxypenicillin anilides (I) and (II) [formula: see text] with beta-lactamase 1 from Bacillus cereus, three distinct processes are observed. The inhibitors act as (a) substrates, the turnover of which respectively results in a single product, namely 6-substituted 2(H)-3,4-dihydro-1,4-thiazine, (b) a transiently inhibited enzyme complex, and finally (c) an irreversibly inactivated enzyme complex. Although differing only in their stereochemistry at one centre, the anilide (K) is a more potent irreversible inactivator of beta-lactamase I than is compound (II). Analysis of irreversibly inactivated beta-lactamase I by isoelectric focusing and inspection of peptide fragmentation maps indicated that irreversible inactivation appears to be accompanied by covalent modification. These studies reveal that the chlorinated 6-spiroepoxypenicillin anilide (I) is a mechanism-based beta-lactamase inhibitor.
authors.affiliation: Department of Pharmaceutical Sciences, University of Nottingham, U.K.
authors.forename: L
authors.initials: L
authors.lastname: Gledhill
authors.forename: P
authors.initials: P
authors.lastname: Williams
authors.forename: B W
authors.initials: BW
authors.lastname: Bycroft
mesh_terms: D001409:Bacillus cereus / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D004795:Enzyme Stability; D006868:Hydrolysis; D007525:Isoelectric Focusing; D007700:Kinetics; D010405:Penicillinase / Q000737:chemistry; D010406:Penicillins / Q000494:pharmacology*; D011487:Protein Conformation; D013379:Substrate Specificity / Q000187:drug effects; D065093:beta-Lactamase Inhibitors
chemical_list: D010406:Penicillins; D065093:beta-Lactamase Inhibitors; C069697:3-chloro-3',3'-dimethyl-7'-oxo-3-((phenylamino)carbonyl)spiro(oxirane-2,6'-(4)thia(1)azabicyclo(3.2.)heptane)-2'-carboxylic acid; D010405:Penicillinase