The Sources of Reactive Oxygen Species and Its Possible Role in the Pathogenesis of Parkinson’s Disease
Table 1
Antioxidant defense systems and proposed mechanisms against ROS.
Classifications
Antioxidants
Functions
Enzymatic antioxidant defenses
Superoxide dismutase (SOD)
SOD catalyzes two O2− anions to convert into a molecule of H2O2 and oxygen 2 O2− + 2H+ → H2O2 + O2
Glutathione peroxidase (GPx)
GPx, a family of multiple isoenzymes containing selenium, catalyzes the degradation of H2O2 and lipid peroxides. Moreover, GPx can utilize GSH as an electron donor for the reduction of peroxides [64].
Catalase (GPx)
Catalase, mainly existing in peroxisomes, is responsible for converting H2O2 into water 2 H2O2 → 2 H2O + O2
Nonenzymatic antioxidants
Ascorbic acid (vitamin C)
Vitamin C, a water-soluble antioxidant, is capable of removing ROS by electron transfer. In addition, vitamin C can act as a cofactor for antioxidant enzymes [88]; [90]
α-Tocopherol (vitamin E)
Vitamin E, a lipid-soluble antioxidant, can attenuate the effects of peroxide. In particular, it can protect against lipid peroxidation in cell membranes [88]
Glutathione (GSH)
GSH, in its reduced form, is known to react with ROS for the removal of ROS. Moreover, GSH is the electron donor for the reduction of peroxides in the GPx reaction [64]
