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Antimicrobial Agents and Chemotherapy, October 2005, p. 4240-4246, Vol. 49, No. 10
0066-4804/05/$08.00+0 doi:10.1128/AAC.49.10.4240-4246.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Centre d'Ingénierie des Protéines, Université de Liège, Sart Tilman, Belgium,1 Department of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan,2 Department of Microbiology, Toho University School of Medicine, 5-21-16 Omorinishi, Ota-ku, Tokyo 1438540, Japan3
Received 1 March 2005/ Returned for modification 17 May 2005/ Accepted 13 July 2005
The heterologous production in Escherichia coli, the purification, and the kinetic characterization of four plasmid-encoded class C ß-lactamases (ACT-1, MIR-1, CMY-2, and CMY-1) were performed. Except for their instability, these enzymes are very similar to the known chromosomally encoded AmpC ß-lactamases. Their kinetic parameters did not show major differences from those obtained for the corresponding chromosomal enzymes. However, the Km values of CMY-2 for cefuroxime, cefotaxime, and oxacillin were significantly decreased compared to those of the chromosomal AmpC enzymes. Finally, the susceptibility patterns of different E. coli hosts producing a plasmid- or a chromosome-encoded class C enzyme toward ß-lactam antibiotics are mainly due to the overproduction of the ß-lactamase in the periplasmic space of the bacteria rather than to a specific catalytic profile of the plasmid-encoded ß-lactamases.
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