Limits...
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.

Show MeSH

Related in: MedlinePlus

Alignment of peptide sequences of Torpedo AChE, Human BChE, Medaka (O. latipes) AChE and Atypical BChE.Numbering of the amino acid sequences is indicated on the right and starts with the amino acids of the mature polypeptide. Conserved (*) and similar (:.) residues are indicated. Locations of the three elements of the catalytic triad are indicated (•). Single underlines link the cysteines participating in intrachain disulfide bond. Sites of conserved aromatic amino acids lining the catalytic gorge in AChE are indicated with↓or↑; those not conserved in medaka (O. latipes) atypical BChE are marked with↑.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3045457&req=5

pone-0017396-g001: Alignment of peptide sequences of Torpedo AChE, Human BChE, Medaka (O. latipes) AChE and Atypical BChE.Numbering of the amino acid sequences is indicated on the right and starts with the amino acids of the mature polypeptide. Conserved (*) and similar (:.) residues are indicated. Locations of the three elements of the catalytic triad are indicated (•). Single underlines link the cysteines participating in intrachain disulfide bond. Sites of conserved aromatic amino acids lining the catalytic gorge in AChE are indicated with↓or↑; those not conserved in medaka (O. latipes) atypical BChE are marked with↑.

Mentions: Two expressed sequences for ChEs are present in the O. latipes genome: AChE (GenBank EST DK110600) and an enzyme that we are classifying as an atypical BChE [45] (GenBank cDNAs AV668390 and GU797251). The sequence for the AChE is truncated near the carboxyl terminus and contains 561 amino acids. The sequence of the mature polypeptide for the atypical BChE from O. latipes contains 564 amino acids (Fig. 1). Pair-wise BLAST alignments of sequences from the catalytic region of ChEs show that the AChE from O. latipes clearly resembles T. californica AChE rather than Homo sapiens BChE (68/80% identity/similarity to AChE compared to 54/70% for BChE), while the atypical BChE resembles both AChE and BChE more or less equally (46/68% for AChE and 49/67% for BChE). A phylogenetic tree of vertebrate and deuterostome invertebrate ChEs is shown in Fig. 2; the AChE of O. latipes is found in the AChE clade, while the atypical BChE of O. latipes is found in the BChE clade.


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 Torpedo AChE, Human BChE, Medaka (O. latipes) AChE and Atypical BChE.Numbering of the amino acid sequences is indicated on the right and starts with the amino acids of the mature polypeptide. Conserved (*) and similar (:.) residues are indicated. Locations of the three elements of the catalytic triad are indicated (•). Single underlines link the cysteines participating in intrachain disulfide bond. Sites of conserved aromatic amino acids lining the catalytic gorge in AChE are indicated with↓or↑; those not conserved in medaka (O. latipes) atypical BChE are marked with↑.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0017396-g001: Alignment of peptide sequences of Torpedo AChE, Human BChE, Medaka (O. latipes) AChE and Atypical BChE.Numbering of the amino acid sequences is indicated on the right and starts with the amino acids of the mature polypeptide. Conserved (*) and similar (:.) residues are indicated. Locations of the three elements of the catalytic triad are indicated (•). Single underlines link the cysteines participating in intrachain disulfide bond. Sites of conserved aromatic amino acids lining the catalytic gorge in AChE are indicated with↓or↑; those not conserved in medaka (O. latipes) atypical BChE are marked with↑.
Mentions: Two expressed sequences for ChEs are present in the O. latipes genome: AChE (GenBank EST DK110600) and an enzyme that we are classifying as an atypical BChE [45] (GenBank cDNAs AV668390 and GU797251). The sequence for the AChE is truncated near the carboxyl terminus and contains 561 amino acids. The sequence of the mature polypeptide for the atypical BChE from O. latipes contains 564 amino acids (Fig. 1). Pair-wise BLAST alignments of sequences from the catalytic region of ChEs show that the AChE from O. latipes clearly resembles T. californica AChE rather than Homo sapiens BChE (68/80% identity/similarity to AChE compared to 54/70% for BChE), while the atypical BChE resembles both AChE and BChE more or less equally (46/68% for AChE and 49/67% for BChE). A phylogenetic tree of vertebrate and deuterostome invertebrate ChEs is shown in Fig. 2; the AChE of O. latipes is found in the AChE clade, while the atypical BChE of O. latipes is found in the BChE clade.

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