Superoxide dismutase defence mechanisms

Superoxide dismutases (SOD EC 1.15.1.1) constitute a group of metalloisoenzymes that neutralise the very reactive superoxide radical, generated in the cell as a by-product of the reduction of molecular oxygen (Salin, 1988). SOD is a highly efficient enzyme system involved in the cellular antioxidant system (cf. section on defence mechanisms). 

There is considerable body of (indirect) evidence which makes oxidative stress one of the best accepted hypothesis for explaining the cause of Parkinson s disease. For example, the Fe(II)/Fe(III) ratio in the substantia nigra is shifted from 2 1 in the normal brain to 1 2 in Parkinsonian brain.131,132 In the Parkinsonian brain several enzymes which constitute the antioxidative defence mechanisms (glutathione peroxidase, catalase) have a decreased activity, while the activity of superoxide dismutase is increased, relative to the normal brain.133 Furthermore, specific products of radical damage, such as lipid hydroperoxides, were detected at a 10-fold increased level in the Parkinsonian brain.134... 

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