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J Biol Chem, Vol. 274, Issue 14, 9312-9319, April 2, 1999
Cloning, Expression, and Properties of a Nonneuronal Secreted
Acetylcholinesterase from the Parasitic Nematode Nippostrongylus
brasiliensis
Ayman S.
Hussein,
Matilde R.
Chacón,
Angela M.
Smith,
Rafael
Tosado-Acevedo, and
Murray E.
Selkirk
From the Department of Biochemistry, Imperial College of Science,
Technology and Medicine, London SW7 2AY, United Kingdom
We have isolated a full-length cDNA encoding
an acetylcholinesterase secreted by the nematode parasite
Nippostrongylus brasiliensis. The predicted protein is
truncated in comparison with acetylcholinesterases from other organisms
such that the carboxyl terminus aligns closely to the end of the
catalytic domain of the vertebrate enzymes. The residues in the
catalytic triad are conserved, as are the six cysteines which form the
three intramolecular disulfide bonds. Three of the fourteen aromatic
residues which line the active site gorge in the Torpedo enzyme are
substituted by nonaromatic residues, corresponding to Tyr-70 (Thr),
Trp-279 (Asn), and Phe-288 (Met).
High level expression was obtained via secretion from Pichia
pastoris. The purified enzyme behaved as a monomeric hydrophilic species. Although of invertebrate origin and possessing the above substitutions in the active site gorge residues, the enzyme efficiently hydrolyzed acetylthiocholine and showed minimal activity against butyrylthiocholine. It displayed excess substrate inhibition with acetylthiocholine at concentrations over 2.5 mM and was
highly sensitive to both active site and "peripheral" site
inhibitors. Northern blot analysis indicated a progressive increase in
mRNA for AChE B in parasites isolated from 6 days postinfection.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.

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Copyright © 1999 by the American Society for Biochemistry and Molecular Biology.
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