The rate of thermal inactivation of Torpedo acetylcholinesterase is not reduced in the C231S mutant

Erica J. Wilson, Jean Massoulié, Suzanne Bon, Terrone L. Rosenberry

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14 Scopus citations


The rate of thermal inactivation of Torpedo AChE at pH 8.5 was increased by the sulfhydryl reagent 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), At 30°C or 37°C, inactivation rates with 0.3 mM: DTNB increased about 5-fold for the wild-type enzyme and for two site-specific mutants, D72S and V129R. The reversible active: site inhibitor, ambenonium, completely stabilized the wild type enzyme and partially stabilized the D72S mutant. However, ambenonium did not protect against the destabilization introduced by DTNB, which still accelerated inactivation of D72S 5-fold. When the only free sulfhydryl group in AChE was removed by replacing cysteine 231 with serine, increased rates of thermal inactivation were observed. The inactivation rate increased by a factor of 2 to 3 for the single mutant (C231S) and by a factor of 5 for the double mutant V129R/C231S. Even in the C231S mutants, DTNB still had an additional effect. It increased the inactivation rate for C231S and V129R/C231 by a factor of about 1.5 to 3 beyond the rates seen in the absence of DTNB. Therefore, at least part of the destabilization seen with DTNB in enzymes that retain C231 does not involve reaction of DTNB with C231.

Original languageEnglish (US)
Pages (from-to)161-164
Number of pages4
JournalFEBS Letters
Issue number2
StatePublished - Jan 29 1996


  • Acetylcholinesterase
  • Disulfide reagent
  • Site-specific mutagenesis
  • Thermal inactivation

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology


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