title: Enol-to-keto tautomerism of peptide groups.
abstract: Density functional based simulations, performed on polyglycine containing an enol peptide group [-C(OH)N-] which is a structural isomer of a keto form [-CONH-], show that in the enol-to-keto tautomeric reaction, the enol peptide group is less stable than the keto form, and that the enol-to-keto tautomerism is characterized by a cis/trans isomerization of the C-N peptide bond. The rate-limiting step in the cis/trans isomerization is a hydrogen migration from O to N atoms in the peptide group with a transition state consisting of a four-membered ring in the cis configuration. An analysis of the cis/trans isomerization pathway shows that the mechanisms for the cis/trans isomerization are essentially different between the enol and keto forms.
authors.affiliation: Institute of Physics and Center for Computational Sciences, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8571, Japan. kkamiya@comas.frsc.tsukuba.ac.jp
authors.forename: Katsumasa
authors.initials: K
authors.lastname: Kamiya
authors.forename: Mauro
authors.initials: M
authors.lastname: Boero
authors.forename: Kenji
authors.initials: K
authors.lastname: Shiraishi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Oshiyama
mesh_terms: D000595:Amino Acid Sequence; D003198:Computer Simulation; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D010455:Peptides