Basic peroxidases in cell walls of plants belonging to the Asteraceae family

A strongly basic peroxidase, which shows oxidase activity and has a visible absorption spectrum typical of haem-containing high-spin ferric secretory plant peroxidases, has been previously characterized in cell walls of Zinnia elegans hypocotyls. This strongly basic peroxidase is also present in intercellular washing-fluids of other species belonging to the family of Asteraceae, such as Helianthus annuus (sunflower), Helianthus debilis, Calendula officinalis, Cosmos bipinnanthus and Tagetes patula, and it has been localised, from its differential syringaldazine oxidase activity, in the lignin forming xylem of H. annuus hypocotyls. The cell wall localisation of this strongly basic peroxidase isoenzyme has been confirmed by subcellular fractionation studies, which showed that it is contained in the ionically and covalently bound fraction. This localisation is in accordance with the role proposed for this isoenzyme in cell wall assembly and lignification.