Purification and characterization of an abscisic acid-inducible anionic peroxidase associated with suberization in potato (Solanum tuberosum)

Abstract

An anionic peroxidase (EC 1.11.1.7), thought to be involved in suberization, was purified 110-fold from wound-healing slices of Solanum tuberosum by a combination of ammonium sulfate fractionation, Sephadex G-100 gel filtration, isoelectric focusing, and phenyl-Sepharose CL-4B chromatography in 24% yield. The purified enzyme was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and horizontal thin-layer polyacrylamide gel electrophoresis. The molecular weight of the enzyme was estimated to be 47,000 by both Sephadex G-100 gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This peroxidase was found to be a glycoprotein containing about 17% carbohydrate, approximately one-quarter of which was shown to be glucosamine residues. It was found to have an isoelectric point of 3.15. An anionic peroxidase was also isolated from abscisic acid-treated callus tissue culture of S. tuberosum by the above purification procedure. The two enzymes were shown to be immunologically similar, if not identical, based on their cross-reactivity with rabbit antibody prepared against the peroxidase from wound-healing slices, whereas the major cationic peroxidase from wound-healing slices did not cross-react with this antibody. The anionic enzyme from both sources showed very similar specific activities when assayed with a range of substrates, whereas the specific activities found for the cationic isozyme isolated from wound-healing slices were quite different.