Redox processes of methionine relevant to β-amyloid oxidation and Alzheimer's disease

This minireview gives an overview over the oxidation mechanisms of methionine (Met) relevant for analogous processes which may lead to the oxidation of beta-amyloid (betaA) peptides. The Cu-II-catalyzed oxidation of a C-terminal Met(35) residue in betaA peptides may be a key to the known propensities of these peptides to form H2O2 and free radicals. Though the reduction potentials of Cu-II and Met would seem unfavorable, there are several structural features of betaA, which may promote a one-electron oxidation of Met. The potentially close association of the Met sulfur with the C=O group C-terminal of Ile(31) in the C-terminus of betaA may support the formation of an S-O bonded radical cation intermediate. Evidence for such S-O bond formation has recently been obtained for a model, N-acetylme- thionine amide. Additional support for a potential catalytic role of an oxygen-containing functional group comes from numerous studies with organic model sulfides. (C) 2001 Elsevier Science.