Sulfenic Acid Formation in Human Serum Albumin by Hydrogen Peroxide and Peroxynitrite
Citations Over TimeTop 10% of 2003 papers
Abstract
Human serum albumin (HSA), the most abundant protein in plasma, has been proposed to have an antioxidant role. The main feature responsible for this property is its only thiol, Cys34, which comprises approximately 80% of the total free thiols in plasma and reacts preferentially with reactive oxygen and nitrogen species. Herein, we show that the thiol in HSA reacted with hydrogen peroxide with a second-order rate constant of 2.26 M(-1) s(-1) at pH 7.4 and 37 degrees C and a 1:1 stoichiometry. The formation of intermolecular disulfide dimers was not observed, suggesting that the thiol was being oxidized beyond the disulfide. With the reagent 7-chloro-4-nitrobenzo-2-oxa-1,3-diazol (NBD-Cl), we were able to detect the formation of sulfenic acid (HSA-SOH) from the UV-vis spectra of its adduct. The formation of sulfenic acid in Cys34 was confirmed by mass spectrometry using 5,5-dimethyl-1,3-cyclohexanedione (dimedone). Sulfenic acid was also formed from exposure of HSA to peroxynitrite, the product of the reaction between nitric oxide and superoxide radicals, in the absence or in the presence of carbon dioxide. The latter suggests that sulfenic acid can also be formed through free radical pathways since following reaction with carbon dioxide, peroxynitrite yields carbonate radical anion and nitrogen dioxide. Sulfenic acid in HSA was remarkably stable, with approximately 15% decaying after 2 h at 37 degrees C under aerobic conditions. The formation of glutathione disulfide and mixed HSA-glutathione disulfide was determined upon reaction of hydrogen peroxide-treated HSA with glutathione. Thus, HSA-SOH is proposed to serve as an intermediate in the formation of low molecular weight disulfides, which are the predominant plasma form of low molecular weight thiols, and in the formation of mixed HSA disulfides, which are present in approximately 25% of circulating HSA.
Related Papers
- → Protein sulfenic acid formation: From cellular damage to redox regulation(2011)275 cited
- → Rapid peroxynitrite reduction by human peroxiredoxin 3: Implications for the fate of oxidants in mitochondria(2018)64 cited
- → Peroxynitrite induced structural changes result in the generation of neo-epitopes on human serum albumin(2013)16 cited
- → The Role of Certain Organic Sulfur Compounds as Preventive Antioxidants. II. Activity as Peroxide Decomposers and Effect of Bases(1976)24 cited
- → The microenvironment of the sulfenic acid of human serum albumin: In search of clues for explaining its spontaneous decay(2017)