Horseradish peroxidase (HRP) is a glycoprotein with a molecular weight of ~44 KD. It is isolated from horseradish roots (Amoracia rusticana) and belongs to the ferroprotoporphyrin group of peroxidases. HRP is a single chain polypeptide containing four disulfide bridges. It is a glycoprotein containing 18% carbohydrate. The carbohydrate composition consists of galactose, arabinose, xylose, fucose, mannose, mannosamine, and galactosamine. HRP readily combines with hydrogen peroxide (H2O2), and the resultant [HRP€“H2O2] complex can oxidize a wide variety of chromogenic hydrogen donors. AAT Bioquest offers the largest collection of HRP substrates and conjugates. HRP is widely used as a label for immunoglobulins in many different immunochemistry applications, including ELISA, immunoblotting and immunohistochemistry. HRP can be conjugated to antibodies by several different methods, including glutaraldehyde, periodate oxidation, through disulfide bonds, and also via amino and thiol directed cross-inkers. Our Buccutite™ HRP conjugation technique is by far the most effective method. HRP is the most desired label for antibodies since it is the smallest and most stable of the three most popular enzyme labels (HRP, alkaline phosphatase, and B-galactosidase), and its glycosylation leads to lower non-specific binding. This purified horseradish peroxidase (HRP) is supplied lyophilized as a salt-free powder for reconstitution and use in HRP detections or conjugations.