In our thesis we did a reasearch about antioxidant acitivity of SOD. To get results we used the formula according to SOD kite Assay Cayman. We understood the formula the following way: the more enzyme the higher antioxidant activity. However, during the research we found articles claiming the opposite. How do you understand the formula?
Thanks, Erika.
The instructions in the kit call for you to divide the absorbance of standard A (no enzyme control) by the absorbance for each of the other standards (increasing amounts of enzyme) or samples, to obtain the linearized rate (LR). The standard curve shows a linearly increasing LR with increasing enzyme concentration. This means that the more enzyme you use, the lower the absorbance, and the absorbance is inversely proportional to the enzyme concentration.
This may seem kind of weird, but the reason for it is shown in figure 1. The assay works by detecting the formation of a colored formazan product from a tetrazolium dye due to the action of superoxide radicals, which are formed by the action of xanthine oxidase on xanthine in the presence of oxygen. SOD eliminates these radicals, thereby preventing the formation of the colored product. So, the more SOD enzyme present, the lower the absorbance.
SOD activity is determined by measuring the decrease in superoxide anions (generated by the enzyme xanthine oxidase [XO]). Since superoxide anions interact with the provided WST dye, yielding color at 450 nm, the decrease in the color signal is proportional to SOD inhibition activity. Therefore, you will have a lower absorbance value with more SOD enzyme.
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