title: Peroxidase activity can dictate the in vitro lignin dehydrogenative polymer structure.
abstract: The objective of this study was to assess the influence of the peroxidase/coniferyl alcohol (CA) ratio on the dehydrogenation polymer (DHP) synthesis. The soluble and unsoluble fractions of horseradish peroxidase (HRP)-catalyzed CA dehydrogenation mixtures were recovered in various proportions, depending on the polymerization mode (Zutropf ZT/Zulauf ZL) and HRP/CA ratio (1.6-1100purpurogallin U mmol(-1)). The ZL mode yielded 0-57%/initial CA of unsoluble condensed DHPs (thioacidolysis yields <200micromolg(-1)) with a proportion of uncondensed CA end groups increasing with the HRP/CA ratio (7.2-55.5%/total uncondensed CA). Systematically lower polymer yields (0-49%/initial CA) were obtained for the ZT mode. In that mode, a negative correlation was established between the beta-O-4 content (thioacidolysis yields: 222-660micromolg(-1)) and the HRP/CA ratio. In both modes, decreasing the HRP/CA ratio below 18Ummol(-1) favoured an end-wise polymerization process evidenced by the occurrence of tri-, tetra- and pentamers involving at least one beta-O-4 bond. At low ratio, the unsoluble ZT DHP was found to better approximate natural lignins than DHPs previously synthesized with traditional methods. Besides its possible implication in lignin biosynthesis, peroxidase activity is a crucial parameter accounting for the structural variations of in vitro DHPs.
authors.affiliation: UMR 206 Chimie Biologique, INRA/INA PG, F-78850 Thiverval Grignon, France. mechin@grignon.inra.fr
authors.forename: Valérie
authors.initials: V
authors.lastname: Méchin
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Baumberger
authors.forename: Brigitte
authors.initials: B
authors.lastname: Pollet
authors.forename: Catherine
authors.initials: C
authors.lastname: Lapierre
mesh_terms: D001567:Benzocycloheptenes / Q000378:metabolism; D002853:Chromatography, Liquid; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007700:Kinetics; D008031:Lignin / Q000737:chemistry* / Q000378:metabolism*; D013058:Mass Spectrometry; D010084:Oxidation-Reduction
chemical_list: D001567:Benzocycloheptenes; D008031:Lignin; D006735:Horseradish Peroxidase; C026133:purpurogallin