title: Quantitative evaluation of the role of cysteine and methionine residues in the antioxidant activity of human serum albumin using recombinant mutants.
abstract: The importance of cysteine (Cys) and methionine (Met) residues for the antioxidant activity of human serum albumin (HSA) was investigated using recombinant HSA mutants, in which Cys34 and/or the six Met residues had been mutated to Ala. The scavenging activities of the mutants against five reactive oxygen and nitrogen species were evaluated by a chemiluminescence assay, electron paramagnetic resonance spectroscopy, or a HPLC-flow reactor assay. Our results showed that the contributions of Cys34 and the Met residues to the antioxidant activity of HSA were 61% and 29% against O(2)(•-), 68% and 61% against H(2)O(2), 38% and 6% against HO(•), 36% and 13% against HOCl, and 51% and 1% against (•)NO, respectively. Thus, the findings propose in a direct way that Cys34 plays a more important role than the Met residues in the antioxidant activity of HSA.
authors.affiliation: Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Iwao
authors.forename: Yu
authors.initials: Y
authors.lastname: Ishima
authors.forename: Junji
authors.initials: J
authors.lastname: Yamada
authors.forename: Taishi
authors.initials: T
authors.lastname: Noguchi
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kragh-Hansen
authors.forename: Katsumi
authors.initials: K
authors.lastname: Mera
authors.forename: Daisuke
authors.initials: D
authors.lastname: Honda
authors.forename: Ayaka
authors.initials: A
authors.lastname: Suenaga
authors.forename: Toru
authors.initials: T
authors.lastname: Maruyama
authors.forename: Masaki
authors.initials: M
authors.lastname: Otagiri
mesh_terms: D019943:Amino Acid Substitution; D003545:Cysteine / Q000737:chemistry* / Q000235:genetics; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D006801:Humans; D008715:Methionine / Q000737:chemistry* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D009569:Nitric Oxide / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D012709:Serum Albumin / Q000737:chemistry* / Q000235:genetics
chemical_list: D016166:Free Radical Scavengers; D005609:Free Radicals; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D012709:Serum Albumin; D009569:Nitric Oxide; D008715:Methionine; D003545:Cysteine