Extracellular superoxide dismutase exists as an octamer

FEBS Lett. 2006 Feb 20;580(5):1485-9. doi: 10.1016/j.febslet.2006.01.081. Epub 2006 Feb 2.


Human extracellular superoxide dismutase (EC-SOD) is involved in the defence against oxidative stress induced by the superoxide radical. The protein is a homotetramer stabilised by hydrophobic interactions within the N-terminal region. During the purification of EC-SOD from human aorta, we noticed that material with high affinity for heparin-Sepharose formed not only a tetramer but also an octamer. Analysis of the thermodynamic stability of the octamer suggested that the C-terminal region is involved in formation of the quaternary structure. In addition, we show that the octamer is composed of both aEC-SOD and iEC-SOD folding variants. The presence of the EC-SOD octamer with high affinity may represent a way to influence the local concentration of EC-SOD to protect tissues specifically sensitive to oxidative damage.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aorta / enzymology
  • Dimerization
  • Humans
  • Protein Folding
  • Protein Structure, Quaternary
  • Protein Transport
  • Sepharose / analogs & derivatives
  • Superoxide Dismutase / chemistry*
  • Superoxide Dismutase / metabolism
  • Thermodynamics


  • heparin-sepharose
  • Sepharose
  • SOD3 protein, human
  • Superoxide Dismutase