Purification and characterization of a cationic peroxidase from artichoke leaves.

Peroxidases (PODs) are part of a large group of enzymes associated with cell wall biosynthesis, response to injury, disease, resistance and wound repair. Separation and distribution of soluble peroxidase, ionically bound and covalently bound peroxidases from artichoke leaves (Cynara cardunculus L. subsp. scolymus (L.) Hayek Fiori) was performed. The POD forms were analyzed by SDS-PAGE and stained for peroxidase activity using o-dianisidine as substrate. Among POD isoenzymes a soluble cationic peroxidase (ALSP) not yet described has been partially purified and characterized from artichoke leaves. The enzyme was shown to be a glycoprotein with a molecular weight of 51 KDa and an isoelectric point of about 9. The substrate specificity of the ALSP is characteristic of class III (guaiacol-type) peroxidases. The ALSP was partially purified by ammonium sulfate precipitation, gel filtration, affinity chromatography, AE-HPLC and IEF. The increase of specific activity was 43 times compared to the crude extract as estimated by the guaiacol assay. Three ALSP fragments were sequenced by MS/MS de novo sequencing method.