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

Concentration dependencies for inhibition of ATCh hydrolysis by recombinant BChE from O. latipes.Transfected COS-7 cells producing BChE were extracted in HIS buffer and assayed with ATCh in the presence of various concentrations of inhibitors. Extracts were incubated with inhibitor for 20 minutes prior to being assayed for activity: physostigmine (○), ethopropazine (▾) BW284c51 (•), iso-OMPA (▿). Data were fit to a three-parameter logistic function as described in Materials and Methods.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3045457&req=5

pone-0017396-g006: Concentration dependencies for inhibition of ATCh hydrolysis by recombinant BChE from O. latipes.Transfected COS-7 cells producing BChE were extracted in HIS buffer and assayed with ATCh in the presence of various concentrations of inhibitors. Extracts were incubated with inhibitor for 20 minutes prior to being assayed for activity: physostigmine (○), ethopropazine (▾) BW284c51 (•), iso-OMPA (▿). Data were fit to a three-parameter logistic function as described in Materials and Methods.

Mentions: Since the recombinant enzyme from O. latipes exhibited anomalous kinetic properties, to characterize further this atypical BChE activity, we determined the half maximal inhibitory concentration (IC50) values of the enzyme for the inhibitors physostigmine, which inhibits all ChEs; BW284c51, which inhibits AChE preferentially; and iso-OMPA and ethopropazine, which inhibit BChE preferentially. Physostigmine and ethopropazine inhibit the enzyme at sub-µM concentrations; by contrast, much higher concentrations of BW284c51 and Iso-OMPA are required for inhibition under the conditions tested (Fig. 6; Table 4). This pattern of inhibition is also not characteristic of either AChE or BChE.


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)

Concentration dependencies for inhibition of ATCh hydrolysis by recombinant BChE from O. latipes.Transfected COS-7 cells producing BChE were extracted in HIS buffer and assayed with ATCh in the presence of various concentrations of inhibitors. Extracts were incubated with inhibitor for 20 minutes prior to being assayed for activity: physostigmine (○), ethopropazine (▾) BW284c51 (•), iso-OMPA (▿). Data were fit to a three-parameter logistic function as described in Materials and Methods.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0017396-g006: Concentration dependencies for inhibition of ATCh hydrolysis by recombinant BChE from O. latipes.Transfected COS-7 cells producing BChE were extracted in HIS buffer and assayed with ATCh in the presence of various concentrations of inhibitors. Extracts were incubated with inhibitor for 20 minutes prior to being assayed for activity: physostigmine (○), ethopropazine (▾) BW284c51 (•), iso-OMPA (▿). Data were fit to a three-parameter logistic function as described in Materials and Methods.
Mentions: Since the recombinant enzyme from O. latipes exhibited anomalous kinetic properties, to characterize further this atypical BChE activity, we determined the half maximal inhibitory concentration (IC50) values of the enzyme for the inhibitors physostigmine, which inhibits all ChEs; BW284c51, which inhibits AChE preferentially; and iso-OMPA and ethopropazine, which inhibit BChE preferentially. Physostigmine and ethopropazine inhibit the enzyme at sub-µM concentrations; by contrast, much higher concentrations of BW284c51 and Iso-OMPA are required for inhibition under the conditions tested (Fig. 6; Table 4). This pattern of inhibition is also not characteristic of either AChE or BChE.

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