(Biochemical enzyme catalysts, found in organisms' healthy cells)
Superoxide Dismutase (SOD)- this water-soluble enzyme needs Manganese, Zinc, Copper (marginal to deficient in US diet), depending on location (Zinc-Copper SOD in the cytosol, Manganese SOD in the mitochondria.
• Removes the Superoxide Radical(source ofH2O2 and OH•). By catalyzing the dismutation of O2•- into oxygen and hydrogen peroxide
|
O2•- + O2•- |
→ |
O2 + H2O2 |
|
Mn / ZnCu-SOD |
• Concentration of SOD in mammals is directly proportional to their life span
• Found in the cells' cytoplasm and mitochondria (energy factory)
Catalase (CAT) - found in membranes of eukaryotic cells (thus not in bacteria); Requires Iron to function
• Catalyze decomposition of Hydrogen Peroxide (H2O2 )to oxygen and water
|
2H2O2 |
→ |
O2 + 2H2O |
|
|
CAT |
|
• Highly reactive enzyme found in peroxisomes (cellular organelles containing enzymes)
Glutathione Peroxidase (GPx). Contains and Requires Selenium to function; actually a family of 8 isoforms: Gpx1 (in cytoplasm ofmost all mammalian cells), GPx2 (intestines) GPx3 thru GPx8, each found in specific areas of the body)
- Two main functions (in reactions requiring glutathione (GSH)):
• Catalyze reduction of lipid hydroperoxides (ROOH) to their corresponding alcohols
|
2GSH + ROOH |
→ |
GS-SG + ROH + H2O |
|
|
GPx |
|
• Catalyze reduction of free Hydrogen Peroxide (H2O2) (source of hydroxyl radicals) to water - H2O2 is the preferred substrate of GPx1
|
2GSH + H2O2 |
→ |
GS-SG + 2 H2O |
|
|
GPx |
Without GPx or CAT to remove Hydrogen peroxide, SOD is of little value. To deal with specific problems, such as wound healing, the body produces H2O2, which must then be removed from where it is not needed, to prevent damage. |
