Initial steps of the peroxidase-catalyzed polymerization of coniferyl alcohol and/or sinapyl aldehyde: capillary zone electrophoresis study of pH effect

• Published in: Phytochemistry (Oxford) 2003, Vol.62 (2), p.139-146
• Main Authors: Fournand, David, Cathala, Bernard, Lapierre, Catherine
• Format: Article
• Language: English
• Subjects: Acrolein - analogs & derivatives; Acrolein - chemistry; Acrolein - metabolism; Biological and medical sciences; Chemical Sciences; Coniferyl alcohol; Dehydrodimers; Dehydrogenative polymerization; Dimerization; Electrophoresis, Capillary; Fundamental and applied biological sciences. Psychology; Horseradish peroxidase; Horseradish Peroxidase - metabolism; Hydrogen peroxide; Hydrogen-Ion Concentration; Lignification; Lignin; Lignin - analogs & derivatives; Lignin - chemistry; Lignin - metabolism; Metabolism; Metabolism. Physicochemical requirements; Molecular Structure; Oxidation-Reduction; Phenols - chemistry; Phenols - metabolism; Plant physiology and development; Polymers; Radical coupling reaction; Sinapyl aldehyde; Substrate Specificity; Time Factors
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/S0031-9422(02)00573-3

Capillary zone electrophoresis has been used to monitor the first steps of the dehydrogenative polymerization of coniferyl alcohol, sinapyl aldehyde, or a mixture of both, catalyzed by the horseradish peroxidase (HRP)–H 2O 2 system. When coniferyl alcohol was the unique HRP substrate, three major dimers were observed (β-5, β-β, and β- O-4 interunit linkages) and their initial formation velocity as well as their relative abundance varied with pH. The β- O-4 interunit linkage was thus slightly favored at lower pH values. In contrast, sinapyl aldehyde turned out to be a very poor substrate for HRP except in basic conditions (pH 8). The major dimer observed was the β,β′-di-sinapyl aldehyde, a red-brown exhibiting compound which might partly participate in the red coloration usually observed in cinnamyl alcohol dehydrogenase-deficient angiosperms. Finally, when a mixture of coniferyl alcohol and sinapyl aldehyde was used, it looked as if sinapyl aldehyde became a very good substrate for HRP. Indeed, coniferyl alcohol turned out to serve as a redox mediator (i.e. “shuttle oxidant”) for the sinapyl aldehyde incorporation in the lignin-like polymer. This means that in particular conditions the specificity of oxidative enzymes might not hinder the incorporation of poor substrates into the growing lignin polymer. The effect of pH on the dehydrogenative dimerization of coniferyl alcohol and/or sinapyl aldehyde, using capillary zone electrophoresis as an analytical tool, is reported.