title: Monolignol oxidation by xylem peroxidase isoforms of Norway spruce (Picea abies) and silver birch (Betula pendula).
abstract: 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.
authors.affiliation: Department of Biological and Environmental Sciences, University of Helsinki, P.O. Box 65, Viikki Biocenter, Finland.
authors.forename: Kaisa
authors.initials: K
authors.lastname: Marjamaa
authors.forename: Eija
authors.initials: E
authors.lastname: Kukkola
authors.forename: Taina
authors.initials: T
authors.lastname: Lundell
authors.forename: Pirkko
authors.initials: P
authors.lastname: Karhunen
authors.forename: Pekka
authors.initials: P
authors.lastname: Saranpää
authors.forename: Kurt V
authors.initials: KV
authors.lastname: Fagerstedt
mesh_terms: D029662:Betula / Q000201:enzymology / Q000378:metabolism*; D001704:Biopolymers / Q000378:metabolism; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D017705:Lignans / Q000737:chemistry / Q000378:metabolism*; D008031:Lignin / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000302:isolation & purification / Q000378:metabolism*; D010636:Phenols / Q000378:metabolism; D010666:Phenylpropionates / Q000378:metabolism; D028222:Picea / Q000201:enzymology / Q000378:metabolism*; D052584:Xylem / Q000201:enzymology / Q000378:metabolism
chemical_list: D001704:Biopolymers; D007527:Isoenzymes; D017705:Lignans; D010636:Phenols; D010666:Phenylpropionates; C496130:sinapyl alcohol; D008031:Lignin; C010559:coniferyl alcohol; D010544:Peroxidases