Table 1.

Summarized characteristics of three superoxide dismutases in eukaryotic cells

Isoform	Location	MW/kDa	Assembly of subunits	Metal ion	Ion-delivery related protein
Cu/ZnSOD	cytoplasm, nucleus, mitochondrial membrane	88	homodimer	Cu2+ (catalytic active)	CCS (copper chaperone for SOD1) [11-13]
					GSH (glutatione, secondary chaperone) [14]
				Zn2+ (maintain enzyme stability)	metallotioneins; ZnT (zinc transporter) [15]
MnSOD	mitochondria matrix	32	homotetramer	Mn2+ (catalytic active)	Smf2p (manganese trafficking factor for mitochondrial SOD2)* [16]
					MTM1 (manganese trafficking factor for mitochondrial SOD2)* [17,18]
ECSOD	plasma membrane, extracellular fluids	135	hornotetrarneric glycoprotein	Cu2+ (catalytic active)	Atox1 (antioxidant-1, copper chaperone) [19]
					MNK (Menkes ATPase) [20]
				Zn2+ (maintain enzyme stability)	N/A

^*the metal transporter which is found in Saccharomyces cerevisiae.