Removal of H(2)O(2), oxidation of toxic reductants, biosynthesis and degradation of lignin, suberization, auxin catabolism, response to environmental stresses such as wounding, pathogen attack and oxidative stress. These functions might be dependent on each isozyme/isoform in each plant tissue. Might function as heat shock-like defense protein. May be implicated in the systemic acquired resistance response. 2 a phenolic donor + H2O2 = 2 a phenolic radical donor + 2 H2O Binds 1 heme b (iron(II)-protoporphyrin IX) group per subunit. Binds 2 calcium ions per subunit. A number of isoforms are produced. According to EST sequences. Preferentially expressed in roots and leaves, slightly in stems. Up-regulated during leaf development. Late induced after mechanical wounding. Enhanced expression following incompatible bacterial pathogen attack. Expressed under a diurnal rhythm (circadian clock control). There are 73 peroxidase genes in A.thaliana. Belongs to the peroxidase family. Classical plant (class III) peroxidase subfamily.