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.

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) and belongs to the ferroprotoporphyrin group of peroxidases.. 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. Product P8375, type VI, is an essentially salt free lyophilized powder. It is commonly used to determine amounts of glucose and peroxides in solution. It has been used to study sensory input of cervical spinal cord neurons.

The enzyme has been used to develop a thermostable soybean peroxidase-based biosensor by cross-linking and electrically ′wiring′ the enzyme through a redox-conducting hydrogel to a glassy carbon electrode. It has also been used to assay the oxidation of low density lipoprotein.

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 and hence, it is the most desired label. Also, its glycosylation leads to lower non-specific binding.

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. Known inhibitors are sodium azide, cyanide, L-cystine, dichromate, ethylenethiourea, hydroxylamine, sulfide, vanadate, p-aminobenzoic acid, and Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, and Pb²⁺ ions.