Horseradish peroxidase C (HRPC) is the most studied member of the class III peroxidases. These enzymes occur in higher plants and catalyse the oxidation of phenolic compounds to phenol radicals using hydrogen peroxide which is reduced to water. Since plant peroxidases generally have broad substrate specificity and produce highly reactive radical products which can participate in non-enzymatic reactions, the biological functions of these enzymes have been difficult to verify. They have been proposed to have roles in lignin production and cell wall formation, for example by catalysing the formation of monolignol radicals which subsequently polymerise to lignin, and by catalysing cell wall cross-linking reactions involving ferulic acid.