title: Cys34 adducts of reactive oxygen species in human serum albumin.
abstract: Long-term exposures to reactive oxygen species (ROS) have been linked to scores of chronic diseases. This has motivated interest in oxidation products of the only free cysteine residue (Cys34) of human serum albumin (HSA) as possible biomarkers of ROS exposure. However, Cys34 oxidation products have not been detected in human serum or plasma. Using liquid chromatography-high resolution tandem mass spectrometry, we report accurate masses and molecular compositions of Cys34 oxidation products in the 2432 Da peptide resulting from tryptic digestion of HSA. Peptides containing the expected sulfinic (Cys-SO(2)H) and sulfonic (Cys-SO(3)H) acids, as well as an adduct representing addition of one oxygen atom and loss of two hydrogen atoms, were detected in four archived samples of human plasma and one fresh sample of human serum. We speculate that this latter adduct is a sulfinamide formed by intramolecular reaction between either the Cys34 sulfenic acid (Cys-SOH) or sulfinic acid (Cys-SO(2)H) and the adjacent glutamine residue (Gln33). All three Cys34 adducts were measured in the five human samples with levels decreasing in the order sulfinic acid > (proposed) sulfinamide > sulfonic acid. Parallel measurements of a negative control detected only small amounts of the Cys34 sulfonic acid and the (proposed) sulfinamide and did not detect the sulfinic acid.
authors.affiliation: Center for Exposure Biology, School of Public Health and College of Chemistry, University of California, 50 University Hall, Berkeley, CA 94720-7356, USA.
authors.forename: Hasmik
authors.initials: H
authors.lastname: Grigoryan
authors.forename: He
authors.initials: H
authors.lastname: Li
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Iavarone
authors.forename: Evan R
authors.initials: ER
authors.lastname: Williams
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Rappaport
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000737:chemistry*; D006801:Humans; D010084:Oxidation-Reduction; D010455:Peptides / Q000032:analysis; D017382:Reactive Oxygen Species / Q000737:chemistry*; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D013434:Sulfenic Acids / Q000737:chemistry; D013441:Sulfinic Acids / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry; D053719:Tandem Mass Spectrometry; D014357:Trypsin / Q000378:metabolism
chemical_list: D010455:Peptides; D017382:Reactive Oxygen Species; D012709:Serum Albumin; D013434:Sulfenic Acids; D013441:Sulfinic Acids; D013451:Sulfonic Acids; D014357:Trypsin; D003545:Cysteine