I.U.B.:1.11.1.7

Peroxidase(HRP)isahemoproteincatalyzingtheoxidationbyhydrogenperoxideofanumberofsubstratessuchasascorbate,ferrocyanide,cytochromecandtheleucoformofmanydyes.HRPhasamolecularweightof40kDaandanoptimumpHof7.0.StABIlity:HPOFFisstablefor9-12monthsat2-8°C.HPODisstable2to3yearsat2-8°C.

UnitDefinition:OneWorthingtonUnitdecomposes1µmoleofH₂O₂perminuteat25°C,pH7.0usingaminoantipyrineandphenol.

TechnicalNote:TheRZ(Reinheitzahl)whichistheabsorbanceration,A₄₀₃/A₂₇₅,hasbeenusedasanindicationofpurity.However,Shannonetal.,JBC,241,266(1966)reportthatthisratiofortheisozymesvariesfrom2.50to4.19.This,togetherwiththeinfluenceexertedbybufferandpH,wouldseemtorenderquestionabletheprecisenessofthisratioasacriterionofpurity.

Numerousdifferentmethodologiesareutilizedforthedeterminationofperoxidaseactivity.ListedbelowaresomeapproximateconversionsasdeterminedbyWorthington.
•1Worthingtonunit=4.6o-dianisidineunitspreviouslyusedbyWorthington
•1Worthingtonunit=0.62ABTSunits(µmoleofdyeoxidizedperminute,pH6.0,25°C,1.7mMdye)
•1Worthingtonunit=2ABSTunits(µmoleofdyeoxidizedperminute,pH5.0,25°C,8.7mMdye)
•1Worthingtonunit=0.5guiacolunits(µmoleofguiacoloxidizedperminute,pH7.0,25°C)
•1Worthingtonunit=0.5pyrogalloltopurpogallinunit(mgofproductper20seconds,pH6.0,20°C)
•1Worthingtonunit=5pyrogalloltopurpogallinunits(µmoleofproductperminuteatpH6.0,30°C)