Table 1.
Some examples of RS generation in living organisms.
| Source of RS | Type of RS | Site of Production | Function |
|---|---|---|---|
| Nicotinamide adenine dinucleotide (NADH) dehydrogenase (Complex I) | superoxide | Mitochondria | Electron transport during oxidative phosphorylation. |
| Coenzyme Q (Complex III) | superoxide | Mitochondria | Electron transport during oxidative phosphorylation. |
| Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) | superoxide | Cytosol, membranes of various organelles | Immune response, phagocytosis. |
| Xanthine oxidase | Superoxide, hydrogen peroxide | Liver, intestines | Catalytic conversion of hypoxanthine to xanthine and uric acid. |
| Nitric oxide synthase | Nitric oxide (NO), superoxide | Cytosol, cellular membranes | Synthesis of NO from L-arginine. |
| Myeloperoxidase | Hypochlorous acid | Neutrophils | Synthesis of hypochlorous acid during respiratory burst. |
| 5-lipoxygenase | Indirect action | Immune cells | Leukotriene production, causing NOX stimulation and RS generation. |
| Peroxynitrite production | Peroxynitrite ion | Phagocytes | Produced from superoxide and NO, phagocytosis. |
| Fenton reaction and Haber–Weiss chain | Hydroxyl/hydroperoxyl radicals | Wherever transition metal ions such as iron and copper come in contact with hydrogen peroxide and/or superoxide. | Mostly associated with pathologies. |