• 100% Inhibition by Super Oxide Dismutase (SOD)
• Can detect low concentrations of SOD
• Highly water-soluble formazan dye.
• Applications: colorimetric detection.

To determine SOD activity, several direct and indirect methods have been developed. A common and convenient indirect method utilizes nitroblue tetrazolium (NBT) conversion to NBT-diformazan (formazan dye) via superoxide radical. However, there are several disadvantages to the NBT method, such as poor water solubility of the formazan dye and the interaction with the reduced form of xanthine oxidase. Though cytochrome C is also commonly used for SOD activity detection, its reactivity with superoxide is too high to determine low levels of SOD activity.

Cell Technology’s SOD kit utilizes a water-soluble tetrazolium salt, WST-1 (2-(4-Iodophenyl)- 3-(4-nitrophenyl)-5-(2,4-disulfophenyl)- 2H-tetrazolium, monosodium salt) that produces a highly water-soluble formazan dye upon reduction with a superoxide anion (6). The rate of the reduction with O₂^.- is linearly related to the xanthine oxidase (XO) activity, and is inhibited by SOD, as shown in Figure 1. Therefore, the IC 50 (50% inhibition activity of SOD or SOD-like materials) can be determined by this colorimetric method. Absorbance can be measured at 440nm.

Figure 1 - Inhibition Curve Prepared Using SOD from Bovine Liver

Figure 2 -  SOD ASSAY Reaction

1. Malstrom, B., Andreasson, L., and Reinhammer, B. in The Enzymes. Byer, P., editor. XIIB, Academic Press, New York (1975).

2. Lontz, W., Sirsjo, J., Liu, W., Lindberg, M., Rollman, O., and G. (1976) Int. J. Cancer 17, 62–70. Torma, H. (1995) Free Radical Biol. Med. 18, 349–355.

3. Janero, D. R. (1995) CRC Crit. Revs. Food Sci. Nutr. 35, 65–81

4. Dominguez-Rodriguez, J.R. et al. (2001) Anticancer Res. 21:1869.

5. Zhao, Y. et al. (2001) Antioxid. Redox Signal 3:375.

6. H. Ukeda, A. K. Sarker, D. Kawana and M. Sawamura, Anal. Sci., 15, 353 (1999).