© 2006 Heron Publishing—Victoria, Canada
Monolignol oxidation by xylem peroxidase isoforms of Norway spruce (Picea abies) and silver birch (Betula pendula)
Kaisa Marjamaa (1), Eija Kukkola (1), Taina Lundell (2), Pirkko Karhunen (3), Pekka Saranpää (4) and Kurt V. Fagerstedt (1, 5)
1. Department of Biological and Environmental Sciences, University of Helsinki, P.O. Box 65, Viikki Biocenter, FIN-00014 Helsinki
University, Finland / 2. Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 56, Viikki Biocenter, FIN-00014 Helsinki
University, Finland / 3. Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland / 4. Finnish Forest Research Institute, P.O. Box 18, FIN-01301 Vantaa, Finland / 5. Corresponding author (kurt.fagerstedt@helsinki.fi) / Received June 13, 2005; accepted August 5, 2005; published online February 1, 2006
Summary
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.
