title: Taurine bromamine: a potent oxidant of tryptophan residues in albumin.
abstract: Taurine is the most abundant free amino acid in leukocytes and can react with HOBr to produce taurine bromamine (Tau-NHBr). The aim of this study was to assess the ability of Tau-NHBr to oxidize tryptophan, either free or as a residue in albumin. We have demonstrated that Tau-NHBr is a powerful oxidant for tryptophan. Importantly, in comparison to taurine chloramine, HOCl or HOBr, Tau-NHBr exhibits a degree of selectivity for tryptophan. Oxidation of albumin by Tau-NHBr resulted in emission of light, and the quantum yield was more than 10-fold more efficient than that of the other oxidants. The fluorescence band corresponding to oxidized albumin (λ(ex) 350/λ(em) 450), which is characteristic of the formation of formylkynurenine, was significantly higher in reactions using Tau-NHBr. Excitation of the fluorescent probe 8-anilino-1-naphthalenesulfonate at 295 nm was used to assess the depletion of tryptophan residues in albumin. Results from this experiment further supported a higher efficiency of oxidation of tryptophan residues by Tau-NHBr. Other parameters of protein oxidation, including cysteine depletion and formation of carbonyl groups, were not significantly different between the oxidants tested. In conclusion, these results indicate that Tau-NHBr has a higher affinity for tryptophan residues in proteins.
authors.affiliation: Departamento de Química, Faculdade de Ciências, UNESP-Univ Estadual Paulista, Bauru, SP, Brazil. vfximenes@fc.unesp.br
authors.forename: Valdecir F
authors.initials: VF
authors.lastname: Ximenes
authors.forename: Luiz Marcos
authors.initials: LM
authors.lastname: da Fonseca
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: de Almeida
mesh_terms: D000818:Animals; D001959:Bromates / Q000494:pharmacology; D002417:Cattle; D006801:Humans; D016877:Oxidants / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity; D013654:Taurine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D001959:Bromates; D016877:Oxidants; D012709:Serum Albumin; D013654:Taurine; C052954:N-bromotaurine; D014364:Tryptophan; C027664:hypobromous acid