Superoxide dismutase (SOD, EC 1.15.1.1) is a kind of metalloenzyme widely found in organism. It is an
important oxygen radical scavenger and can catalytic disproportionation of superoxide anion to form H2O2
and O2. SOD is not only the superoxide anion scavenging enzyme, but also the main H2O2 producing
enzyme, which plays an important role in the biological antioxidant system.
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Superoxide anion (O2 ) is produced by xanthine and xanthine oxidase reaction system. O2 can reduce
tetrazolium-1(WST-1) to form a water-soluble yellow formazan dye, which has absorbance in 450 nm.
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SOD can remove O2 and inhibit the formation of the formazan dye. The darker the yellow color of the
reaction solution, the lower the SOD activity. The lighter the yellow color of the reaction solution, the
higher the activity of SOD.
Reagents and Equipments Required but Not Provided:
Spectrophotometer/microplate reader, table centrifuge, water bath/constant temperature foster box,
electronic balance, transferpettor, micro glass cuvette/96 well flat-bottom plate, mortar/ homogenizer, ice
and distilled water.
Operation steps:
I. Sample preparation:
1. Bacteria or cells: collect bacteria or cells into the centrifuge tube, discard supernatant after
centrifugation. It is suggested that 5 million of bacteria or cell amount with 1 mL of Extraction reagent.
Splitting the bacteria or cell with ultrasonication (placed on ice, ultrasonic power 200W, working time 3s,
interval 10s, repeat for 30 times). Centrifuge at 8000 g for 10 minutes at 4℃ to remove insoluble materials,
and take the supernatant on ice before testing.
2. Tissue: it is suggested that 0.1 g of tissue with 1 mL of Extraction reagent and fully homogenized on
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