Protein A is a cell wall constituent of Staphylococcus aureus, with a molecular weight of 56kDa. It possesses five binding domains which interact with heavy chains of immunoglobulins at the Fc or Fab fragment. In response to protein A, the complement system, interferon production, hypersensitivity reactions and cell-mediated cytotoxicity get activated. Horseradish peroxidase is a heme-containing enzyme. In the presence of hydrogen peroxide, the enzyme catalyzes the oxidation of luminol.
