title: Differential effects of cysteine and methionine residues in the antioxidant activity of human serum albumin.
abstract: Antioxidant properties of human serum albumin (HSA) may explain part of its beneficial role in various diseases related to free radical attack. In the present study, the antioxidant role of Cys and Met was studied by copper-mediated oxidation of human low density lipoproteins and by free radical-induced blood hemolysis which essentially assessed metal-chelating and free radical scavenging activities, respectively. Mild conditions were set up to specifically modify Cys and Met residues by N-ethylmaleimide (NEM) and chloramine T treatments, respectively. We found that Met and Cys accounted for 40-80% of total antioxidant activity of HSA. Copper binding to HSA was decreased by about 50% with chloramine T treatment of Met whereas no change was observed after NEM treatment of Cys. Although other amino acid residues are likely to be involved in anti-/prooxidant properties of HSA, from our data, we propose that Cys chiefly works as a free radical scavenger whereas Met mainly acts as a metal chelator.
authors.affiliation: Faculté de Médecine, INSERM U498-Biochimie des Lipoprotéines, Université de Bourgogne, 7, blvd Jeanne d'Arc, BP 87900 21079, Dijon, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Bourdon
authors.forename: Nadine
authors.initials: N
authors.lastname: Loreau
authors.forename: Laurent
authors.initials: L
authors.lastname: Lagrost
authors.forename: Denis
authors.initials: D
authors.lastname: Blache
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002700:Chloramines / Q000494:pharmacology; D003300:Copper / Q000737:chemistry / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry*; D004228:Dithionitrobenzoic Acid / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005033:Ethylmaleimide / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D005609:Free Radicals; D006461:Hemolysis; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism; D008715:Methionine / Q000737:chemistry*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D010618:Phenanthrolines / Q000494:pharmacology; D011485:Protein Binding; D012709:Serum Albumin / Q000737:chemistry*; D013997:Time Factors; D014105:Tosyl Compounds / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D002700:Chloramines; D016166:Free Radical Scavengers; D005609:Free Radicals; D008077:Lipoproteins, LDL; D010618:Phenanthrolines; D012709:Serum Albumin; D014105:Tosyl Compounds; C016300:chloramine-T; C028559:bathocuproine sulfonate; D003300:Copper; D004228:Dithionitrobenzoic Acid; D008715:Methionine; D003545:Cysteine; D005033:Ethylmaleimide; D010100:Oxygen