The apeE Gene of Salmonella typhimurium Encodes an Outer Membrane Esterase Not Present in Escherichia coli

Abstract

Salmonella typhimurium apeR mutations lead to overproduction of an outer membrane-associated N-acetyl phenylalanine β-naphthyl ester-cleaving esterase that is encoded by the apeE gene (P. Collin-Osdoby and C. G. Miller, Mol. Gen. Genet. 243:674–680, 1994). This paper reports the cloning and nucleotide sequencing of the S. typhimurium apeE gene as well as some properties of the esterase that it encodes. The predicted product of apeE is a 69.9-kDa protein which is processed to a 67-kDa species by removal of a signal peptide. The predicted amino acid sequence of ApeE indicates that it is a member of the GDSL family of serine esterases/lipases. It is most similar to a lipase excreted by the entomopathogenic bacterium Photorhabdus luminescens. The Salmonella esterase catalyzes the hydrolysis of a variety of fatty acid naphthyl esters and of C6 to C16 fatty acid p-nitrophenyl esters but will not hydrolyze peptide bonds. A rapid diagnostic test reported to be useful in distinguishing Salmonella spp. from related organisms makes use of the ability of Salmonella to hydrolyze the chromogenic ester substrate methyl umbelliferyl caprylate. We report that the apeE gene product is the enzyme in Salmonella uniquely responsible for the hydrolysis of this substrate. Southern blot analysis indicates thatEscherichia coli K-12 does not contain a close analog ofapeE, and it appears that the apeE gene is contained in a region of DNA present in Salmonella but not in E. coli.

Characterization of an arylesterase from Lactobacillus helveticus CNRZ32

“…The deduced protein sequence of EstA does not exhibit the G-X-S-Y-G motif characteristically observed in eukaryotic and prokaryotic esterases and lipases (Cho and Cronan 1993;Jaeger et al 1994). Also, EstA does not have the G-D-S-L or G-D-S-L-S motifs which represent distinct subfamilies of serine-dependent esterases and lipases (Cho and Cronan 1993;Upton and Buckley 1995;Chang et al 1996;Carinato et al 1998). However, EstA does have a G-X-H motif located 22 residues from the COOH-terminus, which is characteristic of G-D-S-L and G-D-S-L-S type aryl-and thioesterases (Cho and Cronan 1993;Upton and Buckley 1995).…”

“…Alignment of amino acid residues surrounding S10 in EstA with those surrounding putative active-site serine residues from arylesterases, thioesterases and lipases from other sources (Table 4) revealed that EstA is different from the G-X-S-Y-G family and G-D-S-L and G-D-S-L-S subfamilies of esterases and lipases (Cho and Cronan 1993;Jaeger et al 1994;Upton and Buckley 1995;Chang et al 1996;Carinato et al 1998). However, the presence of an Ile residue instead of a Leu residue in position 4 of the G-D-S-L motif suggests that EstA may be more closely associated with the G-D-S-L subfamily of esterases and lipases.…”

Autotransporters with GDSL Passenger Domains: Molecular Physiology and Biotechnological Applications

“…EstA, the autotransporter esterase of P. aeruginosa , shows similarity to ApeE, an outer membrane esterase from S. enterica serovar typhimurium 30 and to Lip‐1, a lipase from Xenorhabdus (Photorhabdus) luminescens ,31 both of which are autotransporter proteins. Additional homologues include phospholipase B from Moraxella bovis ,32 McaP from Moraxella catharralis ,33 EstE from Xanthomonas vesicatoria 34 and EstA from Serratia liquefaciens MG135 (Table 1).…”

“…The mature autotransporter ApeE is a 67 kDa outer membrane esterase that catalyses the hydrolysis of a variety of fatty acid naphthyl esters, and of C6–C16 fatty acid p ‐nitrophenyl esters 30. This enzyme is also responsible for the hydrolysis of the substrate methylumbelliferyl caprylate (MUCAP); this is used in clinical laboratories to distinguish Salmonella strains from other clinically relevant bacteria 30.…”

“…The mature autotransporter ApeE is a 67 kDa outer membrane esterase that catalyses the hydrolysis of a variety of fatty acid naphthyl esters, and of C6–C16 fatty acid p ‐nitrophenyl esters 30. This enzyme is also responsible for the hydrolysis of the substrate methylumbelliferyl caprylate (MUCAP); this is used in clinical laboratories to distinguish Salmonella strains from other clinically relevant bacteria 30. The expression of apeE was induced by phosphate limitation, and was regulated by the phoBR phosphate regulatory system; this indicates that ApeE may be involved in phospholipid metabolism to provide a cellular phosphate source 53…”