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Expression of a single dimeric membrane-bound acetylcholinesterase in Parascaris equorum

  • V. TALESA (a1), R. ROMANI (a1), M. GRAUSO (a1) (a2), G. ROSI (a1) and E. GIOVANNINI (a1)...

Abstract

A single form of cholinesterase was detected in the parasitic nematode Parascaris equorum and purified from a low-salt Triton X-100 extract of whole animals by affinity chromatography on an edrophonium–Sepharose matrix. Based on gel-filtration chromatography, sedimentation analysis and SDS–PAGE, such a cholinesterase is an amphiphilic globular (G2) dimer (125–129 kDa, 6·1 S). It includes some hydrophobic domain other than phosphatidylinositol, which gives auto-aggregation, detergent interaction and also anchors the molecule to the cell membrane. The enzyme, probably functional in cholinergic neurotransmission, is an acetylcholinesterase showing a fairly low substrate specificity with thiocholine esters. Electrostatic interactions seem to play a major role in the catalytic activity. Studies with inhibitors gave complete inhibition with 1 mM eserine, low sensitivity for procainamide and for tetra(monoisopropyl)pyrophosphortetramide as well as higher inhibition with edrophonium chloride and 1,5-bis(4allyldimethylammoniumphenyl)-pentan-3-one dibromide. The enzyme also showed excess-substrate inhibition with acetylthiocholine. No cross-hybridization occurred between the gene(s) encoding acetylcholinesterase in P. equorum and ace-1 from the free-living nematode Caenorhabditis elegans. The expression of a single cholinesterase form in P. equorum, unusual in free-living nematodes, could be due to parasitic life adaptation with resulting reduction of locomotor activity.

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Corresponding author

Corresponding author: Dipartimento di Medicina Sperimentale, Sezione di Biologia Cellulare e Molecolare, Università di Perugia, Via del Giochetto, I-06100 Perugia, Italy. Tel: +39 75 585 3483. Fax: +39 75 585 3491.

Keywords

Expression of a single dimeric membrane-bound acetylcholinesterase in Parascaris equorum

  • V. TALESA (a1), R. ROMANI (a1), M. GRAUSO (a1) (a2), G. ROSI (a1) and E. GIOVANNINI (a1)...

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