Are the SOD kits sensitive enough to detect SOD in Human serum or plasma samples?
The SOD Assay kits are suitable for mammalian cell extracts. The SOD concentration in plasma or serum is very low, and may not be detectable.

How do you differentiate between the different forms of SOD?
The SOD assay can differentiate between the various SOD isozymes: SOD1 (cytosolic Cu/Zn-SOD), SOD2 (mitochondrial Mn-SOD), and SOD3 (extracellular Cu/Zn-SOD).

1. SOD2 can be inactivated by adding 400 µl or 800 µl of ice-cold chloroform/ethanol (37.5/62.5 (v/v)) to 250 µl of erythrocyte lysate or 500 µl of cell/tissue lysate, respectively, shaking for 30 sec, and then centrifuging at 2,500 x g for 10 min. Assay the aqueous upper phase for SOD1 immediately or freeze in aliquots at -80ºC.

2. The addition of cyanide ion to a final concentration of 2 mM inhibits more than 90% of SOD1 and SOD3 activity. SOD2 is unaffected by cyanide.

3. SOD3 is isolated from the extracellular matrix of tissue. SOD3 has been found in serum and in cerebrospinal, ascitic, and synovial fluids.