title: Purification and characterization of peroxidases correlated with lignification in poplar xylem.
abstract: Lignin is an integral cell wall component of all vascular plants. Peroxidases are widely believed to catalyze the last enzymatic step in the biosynthesis of lignin, the dehydrogenation of the p-coumaryl alcohols. As the first stage in identifying lignin-specific peroxidase isoenzymes, the classical anionic peroxidases found in the xylem of poplar (Populus trichocarpa Trichobel) were purified and characterized. Five different poplar xylem peroxidases (PXP 1, PXP 2, PXP 3-4, PXP 5, and PXP 6) were isolated. All five peroxidases were strongly glycosylated (3.6% to 4.9% N-glucosamine), with apparent molecular masses between 46 and 54 kD and pI values between pH 3.1 and 3.8. Two of the five isolated peroxidases (PXP 3-4 and PXP 5) could oxidize the lignin monomer analog syringaldazine, an activity previously correlated with lignification in poplar. Because these isoenzymes were specifically or preferentially expressed in xylem, PXP 3-4 and PXP 5 are suggested to be involved in lignin polymerization.
authors.affiliation: Laboratorium voor Genetica, Departement Genetica, Vlaams Interuniversitair Instituut voor Biotechnologie, Universiteit Gent, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium.
authors.forename: J H
authors.initials: JH
authors.lastname: Christensen
authors.forename: G
authors.initials: G
authors.lastname: Bauw
authors.forename: K G
authors.initials: KG
authors.lastname: Welinder
authors.forename: M
authors.initials: M
authors.lastname: Van Montagu
authors.forename: W
authors.initials: W
authors.lastname: Boerjan
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D006031:Glycosylation; D007526:Isoelectric Point; D007527:Isoenzymes / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008031:Lignin / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000235:genetics / Q000302:isolation & purification; D010544:Peroxidases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014197:Trees / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D000596:Amino Acids; D007527:Isoenzymes; D010446:Peptide Fragments; D008031:Lignin; D010544:Peroxidases