Plays a key role in hydrogen peroxide removal. H2O2 + L-ascorbate = 2 H2O + L-dehydroascorbate Binds 1 heme b (iron(II)-protoporphyrin IX) group per subunit. Detected in bundle sheath cells, the photosynthetic cells that surround the phloem and xylem. By excess light treatment, by wounding and by heat-shock stress. Binds one cation per subunit; probably K(+), but might also be Ca(2+). Belongs to the peroxidase family. Ascorbate peroxidase subfamily.