Specific reaction of Met 35 in amyloid beta peptide with hypochlorous acid

Abstract

The reaction of the amyloid beta peptide (Aβ) with hypochlorous acid and hydroxyl radicals was analysed by spectrophotometry and mass spectrometry. N-acetylmethionine, Aβ25-35 and Aβ1-42 reacted rapidly with hypochlorous acid. The relative reaction rates of N-acetylmethionine and Aβ with hypochlorous acid was in the order N-acetylmethionine > Aβ25-35 > Aβ1-42. While the reaction of Aβ25-35 in the presence of a slight excess of hypochlorous acid resulted in complete conversion of Met35 to Met35 sulphoxide, Aβ1-42 required more than a 4-fold excess of hypochlorous acid for complete conversion of Met35. Identical products were obtained when Aβ25-35 and Aβ1-42 were treated with a hypochlorous acid generating system. Conversion of Met35 to Met35 sulphoxide in Aβ abolished the aggregation of Aβ25-35. Reaction of Aβ with hydroxyl radicals resulted in limited conversion of Met35 to Met35 sulphoxide. The specific reaction of Met35 in Aβ with hypochlorous acid to form Met35 sulphoxide has been analysed.