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  • 标题:Copper, zinc superoxide dismutase catalyzes hydroxyl radical production from hydrogen peroxide
  • 本地全文:下载
  • 作者:M B Yim ; P B Chock ; E R Stadtman
  • 期刊名称:Proceedings of the National Academy of Sciences
  • 印刷版ISSN:0027-8424
  • 电子版ISSN:1091-6490
  • 出版年度:1990
  • 卷号:87
  • 期号:13
  • 页码:5006-5010
  • DOI:10.1073/pnas.87.13.5006
  • 语种:English
  • 出版社:The National Academy of Sciences of the United States of America
  • 摘要:Cu,Zn superoxide dismutase (Cu,Zn-SOD; EC 1.15.1.1 ) is known to be inhibited slowly by H2O2. Using EPR and the spin traps 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) and N-tert-butyl-alpha-phenylnitrone (PBN), we have shown that Cu,Zn-SOD catalyzes the formation of "free" .OH radicals from H2O2 in pH 7.6 bicarbonate buffer. Supporting evidence includes the following: (i) H2O2 and active Cu,Zn-SOD are required to yield significant signals from spin-trap-OH adducts. (ii) With O2-., Cu,Zn-SOD causes the appearance of intense resonance signals due to DMPO-OH adducts. These signals were inhibited strongly by catalase. (iii) With H2O2, Cu,Zn-SOD, and DMPO, radical scavengers formate and azide, but not ethanol, decrease DMPO-OH signals while causing new intense signals due to their corresponding DMPO-radical adducts. Failure of ethanol to quench DMPO-OH signals is discussed in light of the positively charged active channel of the enzyme. (iv) With PBN as a spin trap, ethanol quenches .OH radical signals and yields PBN-trapped hydroxyethyl radical signals. (v) Mn-SOD does not catalyze "free" .OH radical formation and it also exerts no effect on the signals of DMPO-OH adducts when added together with the Cu,Zn-SOD. The capacity of Cu,Zn-SOD to generate "free" .OH radicals from H2O2 may in part explain the biological damage associated with elevated intracellular SOD activity.
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