Purification and characterization of peroxidases correlated with lignification in poplar xylem.
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.
Christensen
J H
JH
Laboratorium voor Genetica, Departement Genetica, Vlaams Interuniversitair Instituut voor Biotechnologie, Universiteit Gent, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium.
Bauw
G
G
Welinder
K G
KG
Van Montagu
M
M
Boerjan
W
W
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
D000596:Amino Acids; D007527:Isoenzymes; D010446:Peptide Fragments; D008031:Lignin; D010544:Peroxidases