{'fraction_non_alphanumeric': 0.046622264509990484, 'fraction_numerical': 0.009514747859181731, 'mean_word_length': 5.8311688311688314, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Irreversible inactivation of beta-lactamase I from Bacillus cereus by chlorinated 6-spiroepoxypenicillins.

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.