Horseradish Peroxidase (HRP) is derived from the root extracts of the horseradish plant. HRP uses H2O2 to oxidize both organic and inorganic compounds. Antibody conjugates, used in ELISA, membrane & IHC applications, biosensors etc. can be developed when coupling HRP to antibodies. HRP is purified by large scale extraction and purification of horseradish roots by means of ultrafiltration, protein precipitation ion exchange and hydrophobic interaction chromatography, resulting in a highly purified, salt free lyophilized product.

In ELISA, the main colorimetric substrate for HRP is TMB (3, 3', 5, 5'-tetramethylbenzidine). TMB produces a deep blue color during the enzymatic degradation of hydrogen peroxide by HRP, and the addition of an appropriate stop solution gives a clear yellow color that absorbs at 450nm.