Dimeric forms of cholinesterase in <i>Sipunculus nudus</i>

Talesa, Vincenzo Nicola; Principato, Giovanni; Giovannini, Elvio; Giovanni, Maria Vittoria Di; Rosi, Gabriella

doi:10.1111/j.1432-1033.1993.tb18031.x

Cited by 25 publications

(5 citation statements)

References 43 publications

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“…In animals, the active AChE has been found in monomeric, disulWde-linked dimeric and tetrameric forms depending on the animal species. Sipunculida (Talesa et al 1993) and Insecta (Gnagey et al 1987;Toutant 1989) produce only the disulWde-linked dimeric form. On the other hand, in cercopithecus monkey brain, multiple populations of AChE having diVerent subunit structures including monomeric, dimeric and tetrametric were found, although not all of the subunits were linked with a disulWde-bond (Liao et al 1993).…”

Section: Discussionmentioning

confidence: 98%

Characterization of trimeric acetylcholinesterase from a legume plant, Macroptilium atropurpureum Urb.

Yamamoto

Oguri

Momonoki

2007

Planta

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We recently identified plant acetylcholinesterases (E.C.3.1.1.7; AChEs) homologous to the AChE purified from a monocotyledon, maize, that are distinct from the animal AChE family. In this study, we purified, cloned and characterized an AChE from a dicotyledon, siratro. The full-length cDNA of siratro AChE is 1,441 nucleotides, encoding a 382-residue protein that includes a signal peptide. This AChE is a disulfide-linked 125-kDa homotrimer consisting of 41-42 kDa subunits, in contrast to the maize AChE, which exists as a mixture of disulfide and non-covalently linked 88-kDa homodimers. The plant AChEs apparently consist of various quaternary structures, depending on the plant species, similar to the animal AChEs. We compared the enzymatic properties of the dimeric maize and trimeric siratro AChEs. Similar to electric eel AChE, both plant AChEs hydrolyzed acetylthiocholine (or acetylcholine) and propionylthiocholine (or propionylcholine), but not butyrylthiocholine (or butyrylcholine), and their specificity constant was highest against acetylcholine. There was no significant difference between the enzymatic properties of trimeric and dimeric AChEs, although two plant AChEs had low substrate turnover numbers compared with electric eel AChE. The two plant AChE activities were not inhibited by excess substrate concentrations. Thus, similar to some plant AChEs, siratro and maize AChEs showed enzymatic properties of both animal AChE and animal BChE. On the other hand, both siratro and maize AChEs exhibited low sensitivity to the AChE-specific inhibitor neostigmine bromide, dissimilar to other plant AChEs. These differences in enzymatic properties of plant AChEs may reflect the phylogenetic evolution of AChEs.

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Section: Discussionmentioning

confidence: 98%

Characterization of trimeric acetylcholinesterase from a legume plant, Macroptilium atropurpureum Urb.

Yamamoto

Oguri

Momonoki

2007

Planta

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“…Chlorpyrifos treatments have not changed the expression pattern of AChE forms in the foot and gill of S. inaequivalvis. Amphiphilic AChE (LST AChE) forms carry out cho-a G 2 linergic functions in several invertebrate groups [2,5,6,11,25]. High levels of LST AChE were expected in foot tissues from S. inaequivalvis.…”

Section: Discussionmentioning

confidence: 99%

Effects of chlorpyrifos on the catalytic efficiency and expression level of acetylcholinesterases in the bivalve mollusk Scapharca inaequivalvis

Romani

Isani

Santis

et al. 2005

Enviro Toxic and Chemistry

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Three acetylcholinesterase (AChE) forms were detected and recovered from foot or gill tissues of the benthonic bivalve mollusk Scapharca inaequivalvis. A study was performed to investigate changes in catalytic and hydrodynamic features of these enzymes, as well as in their expression levels, after a 4-d or a 15-d exposure to a sublethal concentration (0.1 microl/L) of the pesticide chlorpyrifos (CPF). Both considered organs hold, in either CPF-exposed or untreated animals, two nonamphiphilic AChE forms, G2 and G4, which copurified on a procainamide-containing affinity gel and were separated by density gradient centrifugation. A third AChE form, an amphiphilic membrane-anchored G2, was also purified on the same affinity matrix from both organs. All enzymatic forms are true AChEs and are poorly inhibited by CPE They show different increases in the maximum velocity (Vmax) and in the Michaelis constant (Km) values after CPF exposure. Consequently, catalytic efficiency of AChEs, as defined by the ratio Vmax:Km, rises in the gills and drops in the foot. This would produce an overexpression of AChE-specific mRNAs. The effect was longer lasting in the foot. The combined results indicate that overexpression of enzymes in the presence of organophosphate (OP) may be a consequence of OP resistance itself. Again, the resistance of the organism to CPF seem to depend mainly on the resulting increase in AChE content.

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“…In animals, the active AChE was found in monomeric, disulfide-linked dimeric, and tetrameric forms, depending upon the animal species. For example, Sipunculida (Talesa et al, 1993) and Insecta (Gnagey et al, 1987;Toutant 1989) produce only the disulfide-linked dimeric form. The oxidation reduction states of the disulfide bond between the subunits in the maize AChE dimeric form could dominate an enzymatic activity, similar to the cyanide-resistant alternative oxidase.…”

Section: Discussionmentioning

confidence: 99%

Molecular Characterization of Maize Acetylcholinesterase. A Novel Enzyme Family in the Plant Kingdom

et al. 2005

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Acetylcholinesterase (AChE) has been increasingly recognized in plants by indirect evidence of its activity. Here, we report purification and cloning of AChE from maize (Zea mays), thus providing to our knowledge the first direct evidence of the AChE molecule in plants. AChE was identified as a mixture of disulfide-and noncovalently linked 88-kD homodimers consisting of 42-to 44-kD polypeptides. The AChE hydrolyzed acetylthiocholine and propyonylthiocholine, but not S-butyrylthiocholine, and the AChE-specific inhibitor neostigmine bromide competitively inhibited its activity, implying that maize AChE functions in a similar manner as the animal enzyme. However, kinetic analyses indicated that maize AChE showed a lower affinity to substrates and inhibitors than animal AChE. The full-length cDNA of maize AChE gene is 1,471 nucleotides, which encode a protein having 394 residues, including a signal peptide. The deduced amino acid sequence exhibited no apparent similarity with that of the animal enzyme, although the catalytic triad was the same as in the animal AChE. In silico screening indicated that maize AChE homologs are widely distributed in plants but not in animals. These findings lead us to propose that the AChE family, as found here, comprises a novel family of the enzymes that is specifically distributed in the plant kingdom.

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Dimeric forms of cholinesterase in Sipunculus nudus

Cited by 25 publications

References 43 publications

Characterization of trimeric acetylcholinesterase from a legume plant, Macroptilium atropurpureum Urb.

Characterization of trimeric acetylcholinesterase from a legume plant, Macroptilium atropurpureum Urb.

Effects of chlorpyrifos on the catalytic efficiency and expression level of acetylcholinesterases in the bivalve mollusk Scapharca inaequivalvis

Molecular Characterization of Maize Acetylcholinesterase. A Novel Enzyme Family in the Plant Kingdom

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