The site of nonenzymic glycation of human extracellular-superoxide dismutase in vitro

Free Radic Biol Med. 1992 Sep;13(3):205-10. doi: 10.1016/0891-5849(92)90016-a.


The secretory enzyme extracellular-superoxide dismutase (EC-SOD) has affinity for heparin and some other sulfated glycosaminoglycans and is in vivo bound to heparan sulfate proteoglycan. Nonenzymic glycation of EC-SOD, both in vivo and in vitro, is associated with a reduction in heparin affinity, whereas the enzymic activity is not affected. The glycation sites in EC-SOD are further studied in the present article. It is shown that modification of a few of the five lysyl residues of the subunits of the enzyme with trinitrobenzene sulfonic acid nearly abolishes the in vitro glycation susceptibility. From a chymotryptic digest of in vitro glycated EC-SOD, two peptides with affinity for boronate could be isolated. Amino acid sequence analysis showed that both encompassed the carboxyterminal end. epsilon-Glucitol lysine was identified in both peptides at positions 211 and 212. The primary glycation sites in EC-SOD are thus lysine-211 and lysine-212 in the putative heparin-binding domain in the carboxyterminal end.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Chymotrypsin / metabolism
  • Extracellular Space / enzymology*
  • Glycosylation
  • Heparin / metabolism
  • Humans
  • Molecular Sequence Data
  • Peptide Fragments / chemistry
  • Peptide Fragments / metabolism
  • Superoxide Dismutase / chemistry
  • Superoxide Dismutase / metabolism*
  • Trinitrobenzenesulfonic Acid / pharmacology


  • Peptide Fragments
  • Trinitrobenzenesulfonic Acid
  • Heparin
  • Superoxide Dismutase
  • Chymotrypsin