how the ammonium sulphate extract the peroxidase from radish?

Answer 1

First you need to grind or blend the radish in a suitable buffer, to get the soluble proteins released. This mixture will contain the peroxidase, along with many other proteins.
Adding ammonium sulfate reduces the solubility of proteins, but they do not all behave the same. At 20% saturation some of the proteins will precipitate and can be collected. Test this to see if it contains the peroxidase. If not, raise the concentration to 30% and repeat. Eventually you will get a pellet that contains the peroxidase. You may need to adjust the percentages of ammonium sulfate to optimize it for your specific case.