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Evolution of acetylcholinesterase and butyrylcholinesterase in the vertebrates: an atypical butyrylcholinesterase from the Medaka Oryzias latipes.

Pezzementi L, Nachon F, Chatonnet A - PLoS ONE (2011)

Bottom Line: It is effectively inhibited by physostigmine, typical of all ChEs.However, although the atypical BChE is efficiently inhibited by the BChE-specific inhibitor ethopropazine, it is not by another BChE inhibitor, iso-OMPA, nor by the AChE-specific inhibitor BW284c51.The atypical BChE is found as a glycophosphatidylinositol-anchored (GPI-anchored) amphiphilic dimer (G(2) (a)), which is unusual for any BChE.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Birmingham-Southern College, Birmingham, Alabama, United States of America. lpezzeme@bsc.edu

ABSTRACT
Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are thought to be the result of a gene duplication event early in vertebrate evolution. To learn more about the evolution of these enzymes, we expressed in vitro, characterized, and modeled a recombinant cholinesterase (ChE) from a teleost, the medaka Oryzias latipes. In addition to AChE, O. latipes has a ChE that is different from either vertebrate AChE or BChE, which we are classifying as an atypical BChE, and which may resemble a transitional form between the two. Of the fourteen aromatic amino acids in the catalytic gorge of vertebrate AChE, ten are conserved in the atypical BChE of O. latipes; by contrast, only eight are conserved in vertebrate BChE. Notably, the atypical BChE has one phenylalanine in its acyl pocket, while AChE has two and BChE none. These substitutions could account for the intermediate nature of this atypical BChE. Molecular modeling supports this proposal. The atypical BChE hydrolyzes acetylthiocholine (ATCh) and propionylthiocholine (PTCh) preferentially but butyrylthiocholine (BTCh) to a considerable extent, which is different from the substrate specificity of AChE or BChE. The enzyme shows substrate inhibition with the two smaller substrates but not with the larger substrate BTCh. In comparison, AChE exhibits substrate inhibition, while BChE does not, but may instead show substrate activation. The atypical BChE from O. latipes also shows a mixed pattern of inhibition. It is effectively inhibited by physostigmine, typical of all ChEs. However, although the atypical BChE is efficiently inhibited by the BChE-specific inhibitor ethopropazine, it is not by another BChE inhibitor, iso-OMPA, nor by the AChE-specific inhibitor BW284c51. The atypical BChE is found as a glycophosphatidylinositol-anchored (GPI-anchored) amphiphilic dimer (G(2) (a)), which is unusual for any BChE. We classify the enzyme as an atypical BChE and discuss its implications for the evolution of AChE and BChE and for ecotoxicology.

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Alignment of peptide sequences of C-termini of representative vertebrate AChEs and BChEs.Conserved (*) and similar (:.) residues are indicated. Putative Ω-cleavage sites are underlined. Putative hydrophobic transmembrane regions are boldly underlined. H. sapiens (human), F. catus (cat), C. familiaris (dog), M. musculus (mouse), R. norvegicus (rat), X. tropicalis (clawed toad), O. latipes (medaka), G. aculeatus (stickleback), F. rubripes (fugu), T. marmorata, electric ray.
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pone-0017396-g003: Alignment of peptide sequences of C-termini of representative vertebrate AChEs and BChEs.Conserved (*) and similar (:.) residues are indicated. Putative Ω-cleavage sites are underlined. Putative hydrophobic transmembrane regions are boldly underlined. H. sapiens (human), F. catus (cat), C. familiaris (dog), M. musculus (mouse), R. norvegicus (rat), X. tropicalis (clawed toad), O. latipes (medaka), G. aculeatus (stickleback), F. rubripes (fugu), T. marmorata, electric ray.

Mentions: The three pairs of conserved cysteine residues involved in intra-chain disulfide bonding are also found as Cys69-Cys96, Cys257-Cys268, and Cys405-Cys543 in the AChE; and Cys66-Cys93, Cys257-Cys268, and Cys405-Cys520 in the atypical BChE of O. latipes. Another cysteine (Cys540), near the carboxyl terminal that normally mediates inter-chain disulfide bonding, is also conserved in the atypical BChE (Fig. 1). The carboxyl terminus of the enzyme is of the H-type (Fig. 3), characterized by a loosely defined GPI anchor signal, including an ω cleavage/attachment site followed by a stretch of hydrophobic amino acids [51]. The H-peptides show very little sequence homology to one another. We did not find evidence for the existence of T-type carboxyl terminus for the atypical BChE either as a T-exon in the genome or a T-type carboxyl terminus in the ESTS of O. latipes. The truncated AChE is missing its C-terminal sequence.


Evolution of acetylcholinesterase and butyrylcholinesterase in the vertebrates: an atypical butyrylcholinesterase from the Medaka Oryzias latipes.

Pezzementi L, Nachon F, Chatonnet A - PLoS ONE (2011)

Alignment of peptide sequences of C-termini of representative vertebrate AChEs and BChEs.Conserved (*) and similar (:.) residues are indicated. Putative Ω-cleavage sites are underlined. Putative hydrophobic transmembrane regions are boldly underlined. H. sapiens (human), F. catus (cat), C. familiaris (dog), M. musculus (mouse), R. norvegicus (rat), X. tropicalis (clawed toad), O. latipes (medaka), G. aculeatus (stickleback), F. rubripes (fugu), T. marmorata, electric ray.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3045457&req=5

pone-0017396-g003: Alignment of peptide sequences of C-termini of representative vertebrate AChEs and BChEs.Conserved (*) and similar (:.) residues are indicated. Putative Ω-cleavage sites are underlined. Putative hydrophobic transmembrane regions are boldly underlined. H. sapiens (human), F. catus (cat), C. familiaris (dog), M. musculus (mouse), R. norvegicus (rat), X. tropicalis (clawed toad), O. latipes (medaka), G. aculeatus (stickleback), F. rubripes (fugu), T. marmorata, electric ray.
Mentions: The three pairs of conserved cysteine residues involved in intra-chain disulfide bonding are also found as Cys69-Cys96, Cys257-Cys268, and Cys405-Cys543 in the AChE; and Cys66-Cys93, Cys257-Cys268, and Cys405-Cys520 in the atypical BChE of O. latipes. Another cysteine (Cys540), near the carboxyl terminal that normally mediates inter-chain disulfide bonding, is also conserved in the atypical BChE (Fig. 1). The carboxyl terminus of the enzyme is of the H-type (Fig. 3), characterized by a loosely defined GPI anchor signal, including an ω cleavage/attachment site followed by a stretch of hydrophobic amino acids [51]. The H-peptides show very little sequence homology to one another. We did not find evidence for the existence of T-type carboxyl terminus for the atypical BChE either as a T-exon in the genome or a T-type carboxyl terminus in the ESTS of O. latipes. The truncated AChE is missing its C-terminal sequence.

Bottom Line: It is effectively inhibited by physostigmine, typical of all ChEs.However, although the atypical BChE is efficiently inhibited by the BChE-specific inhibitor ethopropazine, it is not by another BChE inhibitor, iso-OMPA, nor by the AChE-specific inhibitor BW284c51.The atypical BChE is found as a glycophosphatidylinositol-anchored (GPI-anchored) amphiphilic dimer (G(2) (a)), which is unusual for any BChE.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Birmingham-Southern College, Birmingham, Alabama, United States of America. lpezzeme@bsc.edu

ABSTRACT
Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are thought to be the result of a gene duplication event early in vertebrate evolution. To learn more about the evolution of these enzymes, we expressed in vitro, characterized, and modeled a recombinant cholinesterase (ChE) from a teleost, the medaka Oryzias latipes. In addition to AChE, O. latipes has a ChE that is different from either vertebrate AChE or BChE, which we are classifying as an atypical BChE, and which may resemble a transitional form between the two. Of the fourteen aromatic amino acids in the catalytic gorge of vertebrate AChE, ten are conserved in the atypical BChE of O. latipes; by contrast, only eight are conserved in vertebrate BChE. Notably, the atypical BChE has one phenylalanine in its acyl pocket, while AChE has two and BChE none. These substitutions could account for the intermediate nature of this atypical BChE. Molecular modeling supports this proposal. The atypical BChE hydrolyzes acetylthiocholine (ATCh) and propionylthiocholine (PTCh) preferentially but butyrylthiocholine (BTCh) to a considerable extent, which is different from the substrate specificity of AChE or BChE. The enzyme shows substrate inhibition with the two smaller substrates but not with the larger substrate BTCh. In comparison, AChE exhibits substrate inhibition, while BChE does not, but may instead show substrate activation. The atypical BChE from O. latipes also shows a mixed pattern of inhibition. It is effectively inhibited by physostigmine, typical of all ChEs. However, although the atypical BChE is efficiently inhibited by the BChE-specific inhibitor ethopropazine, it is not by another BChE inhibitor, iso-OMPA, nor by the AChE-specific inhibitor BW284c51. The atypical BChE is found as a glycophosphatidylinositol-anchored (GPI-anchored) amphiphilic dimer (G(2) (a)), which is unusual for any BChE. We classify the enzyme as an atypical BChE and discuss its implications for the evolution of AChE and BChE and for ecotoxicology.

Show MeSH
Related in: MedlinePlus