Isolation and characterization of carboxylesterase E3 from Salmonella enteriea

Three esterases (Est-) hydrolysing α-naphthyl acetate: Est-E₁, Est-E₃ and Est-E₄ produced by Salmonella enterica serovar Typhimurium, strain LT2 were separated by DEAE chromatography and gel filtration. Est-E₃, the major component of this set of enzymes, clearly differed from the two other esterases by its apparent molecular weight, titration curve, substrate specificity and inactivation. Immunoglobulins raised against Est-E₃ completely neutralized the activity of Est-E₃ but did not react with Est-E₁ or Est-E₄; it showed no cross reaction with carboxylesterase B of Escherichia coli or with carboxylesterases from other enterobacteria. Est-E₃ showed electrophoretic variants which were biochemically and immunologically detected in the seven subspecies of the genus Salmonella . These findings suggest that variants of Est-E₃ are the products of very closely related loci originating from a common ancestral gene. The esterase could be a phylogenetic marker of the genus and a suitable molecular tool for taxonomy and epidemiology.