Peroxidases are an enzymatic group capable of eliminating the hydrogen peroxide. This compound, which is toxic for the majority of the organism, it is being decomposed in water (H2O) and oxigen (O2) by the catalytic activity of the peroxidases (See below).
2H2O2 + peroxidase –> 2H2O+ O2
Some of the surrounding plants have symbiosis with nitrifying bacteria which contains high concentration levels of peroxidase. An example ofm the plants that experiment this type of symbiosis are the ones belonging to the Fabacea or Leguminosae Family like clovers,lentils, peas etc.
On this image you can see the monomer structure of the horse-radish peroxidase.It was obtained from PDB database, accession number 4A5G
How to do it?
If we take the root of the plants described previously (where I live these are the clovers),we can observe small nodules, in which the bacteria are expected to accumulate. If we make an transversal cut on this root part and apply some oxygen peroxide (such as the one used for wounds), we are able to see tiny bubbles. These bubbles correspond to the oxygen released during the decomposition process of the hydrogen peroxide and they indicate the presence of peroxidase in the roots.
This way we have an easy way to test if the plant possesses peroxidase activity or not! If somebody could try it directly on horseradish it would be great.