Table 2.

SOD isoenzymes in mammalian cells

Type	Structure	Distribution	Function
SOD1 (Cu, Zn SOD)	Homodimer; non-disulfide linked	Cytosol	Familial amyotrophic lateral sclerosis (ALS) by mutated SOD1 (Zhang et al., 2007)
SOD2 (MnSOD)	Tetramer, contains a Mn ion bound to one aspartate and three histidine residues	Mitochondria	Protect mitochondria form ROS damage (Kokoszka et al., 2001)
SOD3 (extracellular SOD;EC-SOD)	Tetramer composed of two disulfide-linked dimers	Extracellular space, ~10 fold higher in the essel wall than in other tissues	Regulating the vascular redox state in extracellular space (van Deel et al., 2008)