Copper, zinc superoxide dismutase catalyzes hydroxyl radical production from hydrogen peroxide - PubMed (original) (raw)

Copper, zinc superoxide dismutase catalyzes hydroxyl radical production from hydrogen peroxide

M B Yim et al. Proc Natl Acad Sci U S A. 1990 Jul.

Abstract

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.

PubMed Disclaimer

References

    1. Proc Natl Acad Sci U S A. 1990 Jan;87(1):384-8 - PubMed
    1. J Biol Chem. 1989 Feb 15;264(5):2498-501 - PubMed
    1. Proc Natl Acad Sci U S A. 1990 Jan;87(1):394-8 - PubMed
    1. J Biol Chem. 1969 Nov 25;244(22):6049-55 - PubMed
    1. J Biol Chem. 1972 Aug 10;247(15):4839-42 - PubMed

MeSH terms

Substances

LinkOut - more resources