Identification and characterization of oxidized human serum albumin. A slight structural change impairs its ligand-binding and antioxidant functions.
Human serum albumin (HSA) exists in both reduced and oxidized forms, and the percentage of oxidized albumin increases in several diseases. However, little is known regarding the pathophysiological significance of oxidation due to poor characterization of the precise structural and functional properties of oxidized HSA. Here, we characterize both the structural and functional differences between reduced and oxidized HSA. Using LC-ESI-TOFMS and FTMS analysis, we determined that the major structural change in oxidized HSA in healthy human plasma is a disulfide-bonded cysteine at the thiol of Cys34 of reduced HSA. Based on this structural information, we prepared standard samples of purified HSA, e.g. nonoxidized (intact purified HSA which mainly exists in reduced form), mildly oxidized and highly oxidized HSA. Using these standards, we demonstrated several differences in functional properties of HSA including protease susceptibility, ligand-binding affinity and antioxidant activity. From these observations, we conclude that an increased level of oxidized HSA may impair HSA function in a number of pathological conditions.
Kawakami
Asami
A
Pharmaceutical Research Laboratories, Ajinomoto Co. Inc., Kawasaki, Japan.
Kubota
Kazuyuki
K
Yamada
Naoyuki
N
Tagami
Uno
U
Takehana
Kenji
K
Sonaka
Ichiro
I
Suzuki
Eiichiro
E
Hirayama
Kazuo
K
D000595:Amino Acid Sequence; D000975:Antioxidants / Q000378:metabolism*; D002853:Chromatography, Liquid; D003198:Computer Simulation; D003545:Cysteine / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D006868:Hydrolysis; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D012709:Serum Albumin / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship; D014357:Trypsin / Q000494:pharmacology
D000975:Antioxidants; D008024:Ligands; D010446:Peptide Fragments; D012709:Serum Albumin; D014357:Trypsin; D003545:Cysteine