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Interactions between human extracellular superoxide dismutase C and sulfated polysaccharides
1Department of Clinical Chemistry, Umeå University Hospital, Sweden.
The Journal of Biological Chemistry
|May 25, 1989
Summary
Extracellular superoxide dismutase (EC-SOD) subtype C binds to sulfated glycosaminoglycans (SGAGs), causing partial enzyme inhibition. This binding, involving lysine and arginine residues, suggests EC-SOD retains activity when complexed in vivo.
Area of Science:
- Biochemistry
- Enzymology
- Extracellular matrix interactions
Background:
- Extracellular superoxide dismutase (EC-SOD) subtype C exhibits high heparin affinity.
- EC-SOD C primarily complexes with extracellular sulfated glycosaminoglycans (SGAGs) in vivo.
Purpose of the Study:
- To investigate the impact of SGAGs on EC-SOD C activity and binding.
- To identify the amino acid residues involved in SGAG binding to EC-SOD C.
Main Methods:
- Enzyme activity assays with sulfated polysaccharides.
- Analysis of enzyme complex formation via molecular weight changes.
- Amino acid-specific modification studies (lysine and arginine).
Main Results:
- Sulfated polysaccharides partially inhibited EC-SOD C activity (10-35%).
- Complex formation with heparin increased EC-SOD C's apparent molecular weight.
- Lysine and arginine residues are crucial for SGAG binding; arginine modification also affected enzyme activity.
Conclusions:
- SGAG binding sites on EC-SOD C are distant from the active site.
- In vivo association with SGAGs likely allows EC-SOD to retain significant enzymatic function.
- Arg-186 is proposed as a key residue for both SGAG binding and enzymatic activity.