Haem peroxidases (or heme peroxidases) are haem-containing enzymes that use hydrogen peroxide as the electron acceptor to catalyse a number of oxidative reactions. Most haem peroxidases follow the reaction scheme:

Fe³⁺ + H₂O₂ [Fe⁴⁺=O]R' (Compound I) + H₂O

[Fe⁴⁺O]R' + substrate --> [Fe⁴⁺=O]R (Compound II) + oxidised substrate

[Fe⁴⁺O]R + substrate --> Fe³⁺ + H₂O + oxidised substrate