Mechanism and stoichiometry of 2,2-diphenyl-1-picrylhydrazyl radical scavenging by glutathione and its novel α-glutamyl derivative

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• 作者：Sä ; de Viirlaid ; Riina Mahlapuu ; Kalle Kilk ; Aleksei Kuznetsov ; Ursel Soomets ; Jaak Jä ; rv
• 关键词：Antioxidant activity ; Glutathione ; GSH α ; -glutamyl analog ; DPPH^rc=""http ; //www.sciencedirect.com/scidirimg/entities/rad"" alt=""radical dot"" title=""radical dot"" border=""0""> ; Kinetic mechanism ; Scavenging stoichiometry
• 刊名：Bioorganic Chemistry
• 出版年：2009
• 出版时间：August 2009
• 年：2009
• 卷：37
• 期：4
• 页码：126-132
• 全文大小：443 K

文摘

Kinetic mechanism and stoichiometry of scavenging the 2,2-diphenyl-1-picrylhydrazyl radical by glutathione and its novel analog, containing α-glutamyl residue in place of the γ-glutamyl moiety, were studied using different ratios of reagents. At low concentrations of the peptides, the process was described as a bimolecular reaction obeying the stoichiometric ratio 1:1. However, at excess of peptides the formation of a non-covalent complex between the reagents was discovered and characterized by dissociation constants K = 0.61 mM for glutathione and K = 0.27 mM for the glutathione α-glutamyl analog, respectively. The complex formation was followed by a reaction step that was characterized by the similar rate constant k = 0.02 s⁻¹ for both peptides. Thus, the apparently different antioxidant activity of these two peptides, observed under common assay conditions, was determined by differences in the formation of this non-covalent complex.