Journal Article

Monolignol oxidation by xylem peroxidase isoforms of Norway spruce (<i>Picea abies</i>) and silver birch (<i>Betula pendula</i>)

Kaisa Marjamaa, Eija Kukkola, Taina Lundell, Pirkko Karhunen, Pekka Saranpää and Kurt V. Fagerstedt

in Tree Physiology

Volume 26, issue 5, pages 605-611
Published in print May 2006 | ISSN: 0829-318X
Published online May 2006 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/26.5.605
Monolignol oxidation by xylem peroxidase isoforms of Norway spruce (Picea abies) and silver birch (Betula pendula)

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We partially purified peroxidase isoform fractions from xylem extracts of a gymnosperm, Norway spruce (Picea abies (L.) Karst.), and an angiosperm, silver birch (Betula pendula Roth.), to determine the participation of xylem-localized peroxidases in polymerization of different types of lignin in vivo. Several peroxidase fractions varying in isoelectric point values from acidic to basic were tested for their ability to catalyze the oxidation of the monolignols coniferyl alcohol, sinapyl alcohol and p-coumaryl alcohol in vitro. All of the xylem peroxidases extracted from Norway spruce and most of those from silver birch showed the highest rate of oxidation with coniferyl alcohol in the presence of hydrogen peroxide. The exception was an acidic peroxidase fraction (pI 3.60–3.65) from silver birch that exhibited higher oxidation activity for sinapyl alcohol than for coniferyl alcohol. For the xylem enzyme fractions extracted from silver birch, the ability to oxidize the artificial phenolic substrate syringaldazine coincided with high specific activity for sinapyl alcohol. Therefore, we conclude that the acidic, neutral and basic xylem peroxidases of Norway spruce all function in the synthesis of guaiacyl-type lignin, whereas in silver birch the acidic peroxidases preferentially oxidize sinapyl subunits. The latter provides a mechanism for synthesis of guaiacyl-syringyl lignin typical of tracheid cell walls in angiosperm trees.

Keywords: coniferyl alcohol; guaiacol; lignin biosynthesis; sinapyl alcohol; syringaldazine; xylem differentiation

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry

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