|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.
SOD kit utilizes a water-soluble tetrazolium salt, WST-1
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