Purification and Characterization of a Wound-Inducible Cell Wall Cationic Peroxidase from Carrot Roots

• Published in: Biochemical and biophysical research communications 1996-09, Vol.226 (1), p.254-260
• Main Authors: Nair, Ayyappan R., Showalter, Allan M.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Cell Wall - enzymology; Chromatography, Ion Exchange; DAUCUS CAROTA; Daucus carota - enzymology; Electrophoresis, Polyacrylamide Gel; Enzyme Induction; Isoelectric Focusing; Molecular Sequence Data; Molecular Weight; PEROXIDASAS; Peroxidases - biosynthesis; Peroxidases - isolation & purification; Peroxidases - metabolism; PEROXYDASE; RACINE; RAICES; Space life sciences
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1996.1342

We have isolated a novel cell wall, cationic peroxidase (pI>9.3) from roots of the carrot plant,Daucus carota.The purified isozyme, referred to as CP>9.3, has a molecular mass of 45 kilodaltons and an Reinheitzahl value of 2.3. Amino-acid composition analysis and N-terminal sequencing have been performed with CP>9.3. The N-terminal sequence shows no homology to any sequence in the protein and nucleic acid data banks. CP>9.3 activity is induced by wounding in carrot leaves and petioles; this activity is also present in carrot roots but is unaltered by wounding. Enhanced CP>9.3 activity is seen at 12 hr post-wounding and continues for at least 60 hr in leaves and petioles. Based on studies using cycloheximide, early activation of CP>9.3 is not due tode novoprotein synthesis, but rather to enzyme activation. Temperature and pH optima for CP>9.3 using guaiacol as a substrate have been determined to be 32°C and 4.9.