Keywords :
Anti-Bacterial Agents/metabolism; Apoenzymes/metabolism; Bacteroides fragilis/enzymology; Binding Sites; Cadmium/metabolism/pharmacology; Calorimetry, Differential Scanning; Chelating Agents/pharmacology; Coenzymes/chemistry/pharmacology; Dialysis; Dithiothreitol/pharmacology; Kinetics; Picolinic Acids/pharmacology; Protein Denaturation; Spectrometry, Fluorescence; Substrate Specificity; Thermodynamics; Titrimetry; Zinc/chemistry/metabolism; beta-Lactamases/metabolism; beta-Lactams
Abstract :
[en] The Bacteroides fragilis Zn-beta-lactamase is active with a mono- and a binuclear zinc site. The apoenzyme produced by removal of both Zn ions does not recover full activity upon readdition of Zn2+ in contrast to an active mono-Zn form prepared at pH 6.0. Differences in k(cat) values observed are substrate-dependent implying distinct mechanisms for the mono- and binuclear species. The substrate profile of a Zn,Cd hybrid obtained by selective exchange of one zinc ion is different from that of the Zn2 enzyme with a remarkable 15-fold increased activity with cefoxitin as substrate.
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