Heparin-Affinity of human extracellular-superoxide dismutase in the brain.
Extracellular-superoxide dismutase (EC-SOD) is one of the three SOD isozymes in humans and has affinity for heparin-like sulfated glycosaminoglycans in the extracellular matrix. The C-terminal portion of EC-SOD is responsible for the heparin-affinity of this enzyme, but this portion should be a target of proteinases. Recently, Oury et al. reported that EC-SOD is localized within the cytoplasm of neuronal cells, while this enzyme is found in the extracellular matrix in most other tissues. It has been speculated that the heparin-binding domain of EC-SOD in the brain is sensitive to proteolysis, which may result in a loss of extracellular immunoreactivity. This study was performed to investigate the heparin-affinity of EC-SOD in the human brain. We found that human EC-SOD in brain tissue has high heparin-affinity similar to that in the umbilical cord. Moreover, heparin-affinity of EC-SOD in brain homogenate was not decreased by incubation at 37 degrees C for 72 h. The proteolytic activity in brain homogenate might be less than that in umbilical cord homogenates. The intracellular localization of EC-SOD could contribute to its slow clearance from the brain and maintenance of its physiological functions in the brain.
Adachi
T
T
Laboratory of Clinical Pharmaceutics, Gifu Pharmaceutical University, Japan. adachi@gifu-pu.ac.jp
Yamnamoto
M
M
Hara
H
H
D000328:Adult; D001921:Brain / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D004797:Enzyme-Linked Immunosorbent Assay; D005110:Extracellular Space / Q000201:enzymology; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D013482:Superoxide Dismutase / Q000378:metabolism*
D006493:Heparin; D013482:Superoxide Dismutase