Peroxidasa from horseradish

La RZ (Reinheitszahl) es la relación de absorbancia A₄₀₃/A₂₇₅ determinada a 0,5-1,0 mg/ml en agua desionizada. Es una medida del contenido de hemina, no de la actividad enzimática. Incluso preparaciones con RZ elevada pueden tener una actividad enzimática baja.

Preliminary work shows it to contain at least five isoenzymes.

La peroxidasa de rábano picante se aísla de las raíces de rábano picante (Amoracia rusticana) y pertenece al grupo de ferroprotoporfirina de las peroxidasas. La HRP es un polipéptido monocatenario que contiene cuatro puentes bisulfuro. Es una glucoproteína que contiene un 18 % de carbohidratos. La composición de los carbohidratos consiste en galactosa, arabinosa, xilosa, fucosa, manosa, manosamina y galactosamina dependiendo de la isoenzima específica. Su peso molecular (~44 kDa) incluye la cadena polipeptídica (33 890 dalton), la hemina más Ca²⁺ (~700 dalton) y los carbohidratos (~9 400 dalton). Existen al menos siete isoenzimas de la HRP. El punto isoeléctrico de las isoenzimas de la peroxidasa de rábano picante oscila entre 3,0 y 9,0.

Una unidad de pirogalol formará 1,0 mg de purpurogalina a partir de pirogalol en 20 segundos a pH 6,0 a 20 °C.

Véase más información sobre la peroxidasa en www.sigma-aldrich.com/enzymeexplorer.

Horseradish peroxidase (HRP) is isolated from horseradish roots (Amoracia rusticana). It is used in biochemistry applications such as western blots, ELISA and Immunohistochemistry. Horseradish peroxidase is used to amplify a weak signal and increase detectability of a target molecule, such as a protein. Horseradish peroxidase, product P8250, has been used to study nonoral antigens in inflamed gingiva and Ebola virus glycoprotein toxicity.

The enzyme has been used as a comparison during the peroxidase assay of extract from mature tall fescue leaf blades. It has also been used to measure H₂O₂ production.

HRP readily combines with hydrogen peroxide (H₂O₂) and the resultant [HRP-H₂O₂] complex can oxidize a wide variety of hydrogen donors. The optimal pH is 6.0-6.5 and the enzyme is most stable in the pH range of 5.0-9.0. 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-linkers. It is smaller and more stable than the enzyme labels β-galactosidase and alkaline phosphatase. Hence, it is the most desired label. Also, its glycosylation leads to lower non-specific binding. It is also used for the determination of glucose and peroxides in solution. Sodium azide, cyanide, L-cystine, dichromate, ethylenethiourea, hydroxylamine, sulfide, vanadate, p-aminobenzoic acid, and Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺ ions are found to inhibit the enzyme activity.

When incubated with a substrate, horseradish peroxidase produces a coloured, fluorimetric, or luminescent derivative of the labeled molecule, allowing quantification. Horseradish peroxidase has been shown to slightly reduce the level of inhibition in a cydAB mutant.