The major product ion of S-adenosyl-L-methionine arises from a neighbouring group reaction

Authors

  • Zoe Mein-Ee Barnett,

    1. School of Chemistry, The University of Melbourne, Victoria 3010, Australia
    2. Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Victoria 3010, Australia
    3. ARC Centre of Excellence for Free Radical Chemistry and Biotechnology
    Search for more papers by this author
  • Linda Feketeová,

    1. School of Chemistry, The University of Melbourne, Victoria 3010, Australia
    2. Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Victoria 3010, Australia
    3. ARC Centre of Excellence for Free Radical Chemistry and Biotechnology
    Search for more papers by this author
  • Richard A. J. O'Hair

    Corresponding author
    1. School of Chemistry, The University of Melbourne, Victoria 3010, Australia
    2. Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Victoria 3010, Australia
    3. ARC Centre of Excellence for Free Radical Chemistry and Biotechnology
    • School of Chemistry, The University of Melbourne, Victoria 3010, Australia.
    Search for more papers by this author

  • Part 70 of the series 'Gas Phase Ion Chemistry of Biomolecules'.

Abstract

Previous studies have shown that low-energy collision-induced dissociation (CID) of the important sulfonium ion metabolite S-adenosyl-L-methionine (AdoMet, m/z 399) yields five main product ions: an ion at m/z 250 arising from methionine loss; ions at m/z 102 and 298, which arise via cleavage of the γ C[BOND]S bond of methionine; and ions at m/z 136 and 264, which arise via loss of protonated and neutral adenine, respectively. These metabolomics studies have, however, either totally ignored the mechanisms that govern the formation of the major product ion at m/z 250 (Gellekink H, van Oppenraaij-Emmerzaal D, van Rooij A, Struys EA, den Heijer M, Blom HJ. Clin. Chem. 2005; 51: 1487), or have proposed an oxonium ion structure that must arise via a rearrangement involving a 1,2 hydride shift (Cataldi TRI, Bianco G, Abate S, Mattia D. Rapid Commun. Mass Spectrom. 2009; 23: 3465). Here DFT calculations on a model system are used to examine potential mechanisms for the formation of the major product ion of AdoMet. These calculations suggest that a neighbouring group mechanism is preferred over a 1,2 hydride shift mechanism. Copyright © 2010 John Wiley & Sons, Ltd.

Ancillary