What is "horseradish peroxidase"

n. an enzyme used in immunohistochemistry to label antigens and their antibodies

The enzyme horseradish peroxidase (HRP), found in the roots of horseradish, is used extensively in biochemistry applications primarily for its ability to amplify a weak signal and increase detectability of a target molecule. It is a metalloenzyme with many isoforms, of which the most studied type is C.