Document Detail

Mechanism of hydrogen peroxide-induced Cu,Zn-superoxide dismutase-centered radical formation as explored by immuno-spin trapping: the role of copper- and carbonate radical anion-mediated oxidations.
MedLine Citation:
PMID:  15607903     Owner:  NLM     Status:  MEDLINE    
We have reinvestigated the biochemistry of H2O2-induced Cu,Zn-superoxide dismutase (SOD1)-centered radicals, detecting them by immuno-spin trapping. These radicals are involved in H2O2-induced structural and functional damage to SOD1, and their mechanism of generation depends on copper and/or (bi)carbonate (i.e., CO2, CO3(-2), or HCO3-). First, in the absence of DTPA and (bi)carbonate, Cu(II) was partially released and rebound at His, Cys, and Tyr residues in SOD1 with the generation of protein-copper-bound oxidants outside the SOD1 active site by reaction with excess H2O2. These species produced immuno-spin trapping-detectable SOD1-centered radicals associated with H2O2-induced active site ( approximately 5 and approximately 10 kDa fragments) and non-active site (smearing between 3 and 16 kDa) copper-dependent backbone oxidations and subsequent fragmentation of SOD1. Second, in the presence of DTPA, which inhibits H2O2-induced SOD1 non-active site fragmentation, (bi)carbonate scavenged the enzyme-bound oxidant at the SOD1 active site to produce the carbonate radical anion, CO3*-, thus protecting against active site SOD1 fragmentation. CO3*- diffuses and produces side chain oxidations forming DMPO-trappable radical sites outside the enzyme active site. Both mechanisms for generating immuno-spin trapping-detectable SOD1-centered radicals were susceptible to inhibition by cyanide and enhanced at high pH values. In addition, (bi)carbonate enhanced H2O2-induced SOD1 turnover as demonstrated by an enhancement in oxygen evolution and SOD1 inactivation. These results help clarify the free radical chemistry involved in the functional and structural oxidative damage to SOD1 by H2O2 with the intermediacy of copper- and CO3*--mediated oxidations.
Dario C Ramirez; Sandra E Gomez Mejiba; Ronald P Mason
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Free radical biology & medicine     Volume:  38     ISSN:  0891-5849     ISO Abbreviation:  Free Radic. Biol. Med.     Publication Date:  2005 Jan 
Date Detail:
Created Date:  2004-12-20     Completed Date:  2005-05-19     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8709159     Medline TA:  Free Radic Biol Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  201-14     Citation Subset:  IM    
Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institutes of Health, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA.
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MeSH Terms
Binding Sites
Blotting, Western
Carbon / chemistry*
Catalase / chemistry
Copper / chemistry,  metabolism*
Cysteine / chemistry
DNA Fragmentation
Dose-Response Relationship, Drug
Enzyme-Linked Immunosorbent Assay
Free Radicals*
Histidine / chemistry
Hydrogen Peroxide / chemistry,  pharmacology*
Hydrogen-Ion Concentration
Models, Chemical
Oxidants / chemistry
Oxygen / chemistry,  metabolism*
Pentetic Acid / chemistry
Spin Trapping
Superoxide Dismutase / chemistry,  metabolism*
Superoxides / chemistry
Time Factors
Tyrosine / analogs & derivatives*,  chemistry
Reg. No./Substance:
0/Anions; 0/Free Radicals; 0/Oxidants; 11062-77-4/Superoxides; 52-90-4/Cysteine; 55520-40-6/Tyrosine; 67-43-6/Pentetic Acid; 71-00-1/Histidine; 7440-44-0/Carbon; 7440-50-8/Copper; 7722-84-1/Hydrogen Peroxide; 7782-44-7/Oxygen; 980-21-2/dityrosine; EC; EC Dismutase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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