Viragh_1999_Biochemistry_38_9557

Product analysis of dealkylation in P(S)C(S)-soman-inhibited electric eel acetylcholinesterase (AChE) by GC-MS using the selected ion monitoring mode has been carried out. The instrument was calibrated with pure standards of 2,3-dimethyl-1-butene and 2, 3-dimethyl-2-butene in the gas phase and methylene chloride extracts of 2,3-dimethyl-2-butanol and 3,3-dimethyl-2-butanol from the aqueous phase. The dealkylation in soman-inhibited AChE at pH 5.0 +/- 0.2 and 25 degrees C produces close to 40% alkenes and 50-60% 2, 3-dimethyl-2-butanol. No 3,3-dimethyl-2-butanol could be detected to provide direct evidence of the intervention of a secondary carbenium ion in the reaction path. All the products of the reaction originate from a tertiary carbenium ion. These findings are in good agreement with the results of Michel et al. [(1967) Arch. Biochem. Biophys. 121, 29], which were obtained by countercurrent distribution of tritium-labeled products and their identification by scintillation counting. The early experiments were performed with the mixture of the four soman diastereomers, all labeled with tritium in Calpha.