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Antimicrobial Agents and Chemotherapy, November 2000, p. 3003-3007, Vol. 44, No. 11
Dipartimento di Scienze e Tecnologie
Biomediche, Università degli Studi L'Aquila, I-67100 Coppito,
L'Aquila,1 and Dipartimento di Biologia
Molecolare, Sez. di Microbiologia, Università di Siena, I-53100
Siena,2 Italy, and Laboratoire
d'Enzymologie et Centre d'Ingénierie des Protéines,
Institut de Chimie, Université de Liège, Sart Tilman,
B-4000 Liège, Belgium3
Received 13 January 2000/Returned for modification 5 May
2000/Accepted 8 August 2000
VIM-1 is a new group 3 metallo-
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Purification and Biochemical Characterization of
the VIM-1 Metallo-
-Lactamase
-lactamase recently detected in
carbapenem-resistant nosocomial isolates of Pseudomonas
aeruginosa from the Mediterranean area. In this work, VIM-1 was
purified from an Escherichia coli strain carrying the
cloned blaVIM-1 gene by means of an
anion-exchange chromatography step followed by a gel permeation
chromatography step. The purified enzyme exhibited a molecular mass of
26 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis,
and an acidic pI of 5.1 in analytical isoelectric focusing.
Amino-terminal sequencing showed that mature VIM-1 results from the
removal of a 26-amino-acid signal peptide from the precursor. VIM-1
hydrolyzes a broad array of
-lactam compounds, including penicillins, narrow- to expanded-spectrum cephalosporins, carbapenems, and mechanism-based serine-
-lactamase inactivators. Only monobactams escape hydrolysis. The highest catalytic
constant/Km ratios (>106
M
1 · s
1) were observed with
carbenicillin, azlocillin, some cephalosporins (cephaloridine,
cephalothin, cefuroxime, cefepime, and cefpirome), imipenem, and
biapenem. Kinetic parameters showed remarkable variability with
different
-lactams and also within the various penam, cephem, and
carbapenem compounds, resulting in no clear preference of the enzyme
for any of these
-lactam subfamilies. Significant differences were
observed with some substrates between the kinetic parameters of VIM-1
and those of other metallo-
-lactamases. Inactivation assays carried
out with various chelating agents (EDTA,
1,10-o-phenanthroline, and pyridine-2,6-dicarboxylic acid)
indicated that formation of a ternary enzyme-metal-chelator complex
precedes metal removal from the zinc center of the protein and revealed
notable differences in the inactivation parameters of VIM-1 with
different agents.
*
Corresponding author. Mailing address for Nicola
Franceschini: Dipartimento di Scienze e Tecnologie Biomediche,
Università degli Studi de L'Aquila, Via Vetoio, 67100 L'Aquila,
Italy. Phone: 39 0862 433456. Fax: 39 0862 433433. E-mail:
nicola.franceschini{at}cc.univaq.it.
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