Oxidação de lisozima por haloaminas: caracterização química e efeitos biológicos
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Data
2014-11-07
Autores
Petrônio, Maicon Segalla [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
As proteínas são macromoléculas complexas de alto peso molecular e que desempenham inúmeras funções nas células. Estas funções podem ser comprometidas caso ocorram modificações nas suas estruturas. Fatores físicos e químicos podem provocar estas alterações, inclusive processos oxidativos mediados por espécies reativas de oxigênio. Entre essas modificações destaca-se a formação de proteínas amiloidais que estão relacionadas a diversas doenças como Parkinson e Alzheimer. O ácido hipocloroso (HOCl) e o ácido hipobromoso (HOBr) são oxidantes gerados pela ativação de leucócitos e há abundantes relatos de seus efeitos deletérios sobre proteínas. Nesse contexto, este trabalho teve como objetivo estudar as alterações estruturais e funcionais na proteína lisozima provocadas por sua oxidação através dos ácidos hipo-halosos, HOCl, HOBr e por suas haloaminas, taurina cloramina (Tau-NHCl), taurina bromamina (Tau-NHBr) e taurina dibromamina (Tau-NBr2). A oxidação de lisozima pela adição de Tau-NHBr ou Tau-NBr2 (excesso molar de quatro vezes) causou depleção completa da sua fluorescência intrínseca, entretanto, os ácidos HOCl e HOBr causaram a redução de apenas 40% e 50% respectivamente. Em contraste com o seu precursor, Tau-NHCl, foi incapaz de oxidar a lisozima. As haloaminas foram cerca de duas vezes mais eficazes como inibidores da atividade enzimática do que os seus precursores HOCl e HOBr. Por outro lado, os ácidos foram mais eficazes na promoção da agregação de lisozima, efeito este, evidenciado pelo aumento da turbidez, espalhamento de luz e anisotropia de fluorescência da proteína. Os agregados apresentaram propriedades espectroscópicas que sugeriram a formação de estruturas amiloidais, como foi observado pelo ensaio de Tioflavina T. Em contraste com os ácidos hipo-halosos, as haloaminas foram inibidores parciais da formação de proteínas amiloides. Em conclusão, estes resultados sugerem ...
Proteins are complex macromolecules of high molecular weight and performing numerous functions in cells. These functions may be compromised if there are any modifications in their structures. Physical and chemical factors may cause these changes, including oxidative processes mediated by reactive oxygen species. Among these changes was the formation of amyloid proteins that are related to various diseases such as Parkinson's and Alzheimer's. The hypochlorous acid (HOCl) and hipobromous acid (HOBr) are oxidants generated by the activation of leukocytes and there are abundant reports of their deleterious effects on proteins. In this context this work aimed to study the structural and functional changes in the protein lysozyme caused by their oxidation through hypohalous acids, HOCl, HOBr, and haloamines taurine Chloramine (Tau-NHCl), taurine monobromamine (Tau-NHBr) and taurine dibromamine (Tau-NBr2). The oxidation of lysozyme by addition of Tau-NHBr or Tau-NBr2 (molar excess of four times) caused complete depletion of its intrinsic fluorescence, however, the acids HOCl and HOBr caused a reduction of only 40% and 50% respectively. In contrast to its precursor, Tau-NHCl was unable to oxidise the lysozyme. The haloamines were about twice as effective inhibitors of enzyme activity than their precursors HOCl and HOBr. On the other hand, the acids were more effective in promoting aggregation of lysozyme, this effect, evidenced by increased turbidity, light scattering and fluorescence anisotropy of the protein. The aggregates presented spectroscopic properties that suggested the formation of amyloid structures, as noted by thioflavin t test. In contrast with hypohalous acids, the haloamines were partial formation of protein inhibitors became. In conclusion, these results suggest that HOBr, like their haloamines Tau-NHBr and Tau-NBr2, are selective with regard to oxidation of tryptophan residues in proteins. This particularity directly affects ...
Proteins are complex macromolecules of high molecular weight and performing numerous functions in cells. These functions may be compromised if there are any modifications in their structures. Physical and chemical factors may cause these changes, including oxidative processes mediated by reactive oxygen species. Among these changes was the formation of amyloid proteins that are related to various diseases such as Parkinson's and Alzheimer's. The hypochlorous acid (HOCl) and hipobromous acid (HOBr) are oxidants generated by the activation of leukocytes and there are abundant reports of their deleterious effects on proteins. In this context this work aimed to study the structural and functional changes in the protein lysozyme caused by their oxidation through hypohalous acids, HOCl, HOBr, and haloamines taurine Chloramine (Tau-NHCl), taurine monobromamine (Tau-NHBr) and taurine dibromamine (Tau-NBr2). The oxidation of lysozyme by addition of Tau-NHBr or Tau-NBr2 (molar excess of four times) caused complete depletion of its intrinsic fluorescence, however, the acids HOCl and HOBr caused a reduction of only 40% and 50% respectively. In contrast to its precursor, Tau-NHCl was unable to oxidise the lysozyme. The haloamines were about twice as effective inhibitors of enzyme activity than their precursors HOCl and HOBr. On the other hand, the acids were more effective in promoting aggregation of lysozyme, this effect, evidenced by increased turbidity, light scattering and fluorescence anisotropy of the protein. The aggregates presented spectroscopic properties that suggested the formation of amyloid structures, as noted by thioflavin t test. In contrast with hypohalous acids, the haloamines were partial formation of protein inhibitors became. In conclusion, these results suggest that HOBr, like their haloamines Tau-NHBr and Tau-NBr2, are selective with regard to oxidation of tryptophan residues in proteins. This particularity directly affects ...
Descrição
Palavras-chave
Taurina, Parkinson, Doença de, Alzheimer, Doença de, Proteínas, Macromoleculas, Leucócitos, Bioquímica, Xenobiotica, Biochemistry
Como citar
PETRÔNIO, Maicon Segalla. Oxidação de lisozima por haloaminas: caracterização química e efeitos biológicos. 2014. 89 f. Tese (doutorado) - Universidade Estadual Paulista Julio de Mesquita Filho Faculdade de Ciências Farmacêuticas, 2014.