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Mass spectral evidence for carbonate-anion-radical-induced posttranslational modification of tryptophan to kynurenine in human Cu, Zn superoxide dismutase. Free Radic Biol Med 2004 Dec 15;37(12):2018-26

Date

11/17/2004

Pubmed ID

15544920

DOI

10.1016/j.freeradbiomed.2004.08.026

Scopus ID

2-s2.0-8544240825 (requires institutional sign-in at Scopus site)   34 Citations

Abstract

Previously, we showed that oxidation of tryptophan-32 (Trp-32) residue was crucial for H(2)O(2)/bicarbonate (HCO(3)(-))-dependent covalent aggregation of human Cu,Zn SOD1 (hSOD1). The carbonate anion radical (CO(3)(-))-induced oxidation of Trp-32 to kynurenine-type oxidation products was proposed to cause the aggregation of hSOD1. Here we used the matrix-assisted laser desorption ionization-time of flight mass spectroscopy, high-performance liquid chromatography-electrospray ionization mass spectroscopy, and liquid chromatography mass spectroscopy methods to characterize products. Results show that a peptide region (31-36) of hSOD1 containing the Trp-32 residue (VWGSIK) is oxidatively modified to the N-formylkynurenine (NFK)- and kynurenine (Kyn)-containing peptides (V(NFK)GSIK) and (V(Kyn)GSIK) during HCO(-)-dependent peroxidase activity of hSOD1. Also, UV photolysis of a cobalt complex that generates authentic CO(3)(-) radical induced a similar product profile from hSOD1. Similar products were obtained using a synthetic peptide with the same amino acid sequence (i.e., VWGSIK). We propose a mechanism involving a tryptophanyl radical for CO(3)(-)-induced oxidation of Trp-32 residue (VWGSIK) in hSOD1 to V(NFK)GSIK and V(Kyn)GSIK.

Author List

Zhang H, Joseph J, Crow J, Kalyanaraman B

Author

Balaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Anions
Carbonates
Chromatography, High Pressure Liquid
Copper
Electron Spin Resonance Spectroscopy
Free Radicals
Humans
Kynurenine
Models, Molecular
Oxidation-Reduction
Protein Processing, Post-Translational
Protein Structure, Tertiary
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
Superoxide Dismutase
Tryptophan
Zinc