title: Isolation, characterization, and heterologous expression of a carboxylesterase of Pseudomonas aeruginosa PAO1.
abstract: We purified to homogeneity an intracellular esterase from the opportunistic pathogen Pseudomonas aeruginosa PAO1. The enzyme hydrolyzes p-nitrophenyl acetate and other acetylated substrates. The N-terminal amino acid sequence was analyzed and 11 residues, SEPLILDAPNA, were determined. The corresponding gene PA3859 was identified in the P. aeruginosa PAO1 genome as the only gene encoding for a protein with this N-terminus. The encoding gene was cloned in Escherichia coli, and the recombinant protein expressed and purified to homogeneity. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis and analytical gel filtration chromatography, the esterase was found to be a monomer of approximately 24 kDa. The experimentally determined isoelectric point was 5.2 and the optimal enzyme activity was at 55 degrees C and at pH 9.0. The esterase preferentially hydrolyzed short-chain fatty acids. It is inhibited by phenylmethylsulfonyl fluoride (PMSF) but not by ethylendiaminotetraacetic acid (EDTA). Native enzyme preparations typically showed a Michaelis constant (K(m)) and V(max) of 0.43 mM and 12,500 U mg(-1), respectively, using p-nitrophenyl acetate as substrate. Homology-based database searches clearly revealed the presence of the consensus GXSXG signature motif that is present in the serine-dependent acylhydrolase protein family.
authors.affiliation: International School for Advanced Studies, Alessandro Pesaresi, Via Beirut 2-4, I-34014 Trieste, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pesaresi
authors.forename: Giulia
authors.initials: G
authors.lastname: Devescovi
authors.forename: Doriano
authors.initials: D
authors.lastname: Lamba
authors.forename: Vittorio
authors.initials: V
authors.lastname: Venturi
authors.forename: Giuliano
authors.initials: G
authors.lastname: Degrassi
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D043182:Carboxylesterase / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D007526:Isoelectric Point; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D011994:Recombinant Proteins; D043182:Carboxylesterase
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