title: Facile hydrogen-deuterium exchange at the 5'-position of an analogue of S-adenosyl-l-methionine.
abstract: S-3',4'-anhydroadenosyl-l-methionine is an analogue of the S-adenosyl-l-methionine coenzyme. Here we report on a rapid solvent exchange of the methylene protons at the 5'-position of this analogue. The rate of H/D exchange was measured by nuclear magnetic resonance spectroscopy under buffered conditions in deuterium oxide. The reaction is specific base catalyzed and displays a second-order rate constant of 2 x 10(4) M(-1) s(-1), which corresponds to a rate enhancement of 10(12) compared to solvent exchange of alpha-methylene protons in acyclic, aliphatic sulfonium ions. No other carbon bonded hydrogens in the molecule exchange with solvent under the experimental conditions. Allylic stabilization of a carbanionic-like transition state for the solvent exchange process can account for these results. Solvent exchange under these mild conditions provides a simple way to prepare a 5'-2H-labeled form of the coenzyme analogue.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, 1710 University Avenue, 53705, USA.
authors.forename: Olafur Th
authors.initials: OT
authors.lastname: Magnusson
authors.forename: Perry A
authors.initials: PA
authors.lastname: Frey
mesh_terms: D003903:Deuterium / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D007700:Kinetics; D008968:Molecular Conformation; D015394:Molecular Structure; D012436:S-Adenosylmethionine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: C455845:S-3',4'-anhydroadenosylmethionine; D012436:S-Adenosylmethionine; D006859:Hydrogen; D003903:Deuterium