What is the role of PVP (Polyvinylpyrrolidone), when we use it in phosphate buffer for antioxidant enzymes activity assays? such as assay of SOD or POD activity in plant cell....
It's probably there to inhibit the action of polyphenol oxidase enzymes and/or absorb resulting polyphenols from the plant cells that would cause inhibition of the other enzymes.
Certain antioxidant enzymes are sensitive to interference from polyphenols present in biological samples. PVP has the ability to bind to polyphenolic compounds, preventing them from interfering with the assay.