Horseradish peroxidase (HRP)

Horseradish peroxidase (HRP) is a large, heme-containing glycoprotein primarily derived from the roots of the plant Armoracia rusticana. While it is most commonly recognized for its ubiquitous role in molecular biology as a diagnostic reporter enzyme, HRP is increasingly investigated as a therapeutic agent in the field of oncology. Its primary biochemical function involves the reduction of hydrogen peroxide to water, coupled with the oxidation of a wide variety of organic and inorganic substrates. In medical applications, HRP is the central component of Enzyme-Prodrug Therapy (EPT), where it is targeted to tumor cells to convert non-toxic precursors, most notably indole-3-acetic acid, into potent cytotoxic metabolites. These metabolites, such as peroxyl and oxindolyl radicals, cause extensive DNA damage and lipid peroxidation, leading to localized cell death. The therapeutic challenge associated with HRP remains its potential immunogenicity in humans and the requirement for localized delivery to minimize systemic toxicity.

Other names

Armoracia rusticana peroxidaseHRP-CDonor:hydrogen-peroxide oxidoreductase

Horseradish peroxidase catalyzes the oxidation of various substrates using hydrogen peroxide as an electron acceptor. In therapeutic contexts, such as Gene-Directed Enzyme Prodrug Therapy (GDEPT), it oxidizes non-toxic prodrugs like indole-3-acetic acid (IAA) into cytotoxic radical species that induce oxidative stress and apoptosis in target cells.