Horseradish peroxidase 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 depending upon the specific isozyme. Its molecular weight (~44 kDa) includes the polypeptide chain (33,890 Daltons), hemin plus Ca²⁺ (~700 Daltons), and carbohydrate (~9,400 Daltons). At least seven isozymes of HRP exist. The isoelectric point for horseradish peroxidase isozymes ranges from 3.0 - 9.0.

Peroxidase from horseradish has been used in a study with dehydrogenative polymers (DHP) to investigate the monolignol coupling mechanism. It has also been used to help develop a colorimetric method for microRNA (miRNA) detection by creating a horseradish peroxidase-mimicking DNAzyme.

Horseradish peroxidase has been shown to catalyze the polymerization of various substances including acetaminophen and cardanol.

Maintains activity at low pH and higher temperature.

One pyrogallol unit will form 1.0 mg purpurogallin from pyrogallol in 20 sec at pH 6.0 at 20 °C.

Stabilized by chemical protection of the primary amines.

The RZ (Reinheitszahl) is the absorbance ratio A₄₀₃/A₂₇₅ determined at 0.5-1.0 mg/ml in deionized water. It is a measure of hemin content, not enzymatic activity. Even preparations with high RZ may have low enzymatic activity.

View more information on peroxidase at www.sigma-aldrich.com/enzymeexplorer.