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Antimicrobial Agents and Chemotherapy, February 2003, p. 582-587, Vol. 47, No. 2
0066-4804/03/$08.00+0     DOI: 10.1128/AAC.47.2.582-587.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Biochemical Characterization of the Acquired Metallo-ß-Lactamase SPM-1 from Pseudomonas aeruginosa

Tanya A. Murphy,1* Alan M. Simm,1 Mark A. Toleman,1 Ronald N. Jones,2 and Timothy R. Walsh1

Department of Pathology and Microbiology, University of Bristol, Bristol BS8 1TD, United Kingdom,1 the JONES Group/JMI Laboratories, North Liberty, Iowa2

Received 2 August 2002/ Returned for modification 3 September 2002/ Accepted 31 October 2002

SPM-1 is a new metallo-ß-lactamase recently identified in Pseudomonas aeruginosa strain 48-1997A, isolated in Sao Paulo, Brazil. Kinetic analysis demonstrated that SPM-1 has a broad hydrolytic profile across a wide range of ß-lactam antibiotics. Considerable variation was observed within the penicillin, cephalosporin, and carbapenem subfamilies; however, on the whole, SPM-1 appears to preferentially hydrolyze cephalosporins. The highest kcat/Km ratios (in micromolar per second) overall were observed for this subgroup. The hydrolytic profile of SPM-1 bears the most similarity to that of the metallo-ß-lactamase IMP-1, yet for the most part, SPM-1 has kcat/Km values higher than those of IMP-1. Zinc chelator studies established that progressive inhibition of SPM-1 by EDTA, dipicolinic acid, and 1-10-o-phenanthroline demonstrated a biexponential pattern in which none of the chelators completely inhibited SPM-1. A homology model of SPM-1 was developed on the basis of the IMP-1 crystal structure, which showed the protein folding and active-site structure characteristic of metallo-ß-lactamases and which provides an explanation for the kinetic profiles observed.

* Corresponding author. Mailing address: Department of Pathology and Microbiology, University of Bristol, Bristol BS8 1TD, United Kingdom. Phone: 44 117 9287897. Fax: 44 117 9287896. E-mail: tanya.murphy{at}bristol.ac.uk.

Antimicrobial Agents and Chemotherapy, February 2003, p. 582-587, Vol. 47, No. 2
0066-4804/03/$08.00+0     DOI: 10.1128/AAC.47.2.582-587.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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