Effects of Arabidopsis thaliana cell walls on dehydrogenative polymers growth reaction using recombinant cationic cell-wall-peroxidase

Abstract Artificial lignin (dehydrogenative polymers: DHPs) has been developed to investigate lignin structures and properties. However, compared with native lignin in plant cell walls, DHPs have lower molecular weight and less content of β- O -4. The conditions required for dehydrogenative polymerization, particularly the reaction within the polysaccharide matrix, are believed to be crucial for promoting lignin growth reaction. In our previous article, xyloglucan esterified with ferulic acid was adsorbed on nematic order cellulose film. Sinapyl alcohol or coniferyl alcohol was polymerized on that film using recombinant cationic cell-wall-peroxidase. The molecular weight and content of β- O -4 of DHPs prepared on artificial cell walls were compared with syringyl-DHP-buffer prepared by polymerizing sinapyl alcohol and guaiacyl-DHP-buffer prepared by polymerizing coniferyl alcohol in buffer by using recombinant cationic cell-wall-peroxidase. DHPs prepared on artificial cell walls had lower molecular weight and less content of β- O -4 than syringyl-DHP-buffer and guaiacyl-DHP-buffer. These results suggested that lignin growth reaction in DHPs preparation on polysaccharide adsorbed on cellulose film may have been inhibited. However, it was considered that the suprastructure of artificial cell walls and plant cell walls is entirely different. This study investigated the effects of Arabidopsis thaliana cell walls on DHPs properties following dehydrogenative polymerization reaction with cell walls. Sinapyl alcohol or coniferyl alcohol was polymerized with Arabidopsis thaliana cell walls using recombinant cationic cell-wall-peroxidase. Syringyl-DHP-buffer and guaiacyl-DHP-buffer were prepared in the buffer and served as comparative controls. Sinapyl alcohol-DHPs prepared with Arabidopsis thaliana cell walls had lower molecular weight and less content of β- O -4 than syringyl-DHP-buffer. Conversely, coniferyl alcohol-DHPs prepared with Arabidopsis thaliana cell walls had slightly higher molecular weight and higher content of β- O -4 compared with guaiacyl-DHP-buffer. These results indicated that the effects of plant cell walls on lignin growth reaction differed between syringyl and guaiacyl monomers. Sinapyl-alcohol-DHPs are strongly adsorbed onto xylan, suggesting that polymerization may be restricted. Conversely, coniferyl-alcohol-DHPs are weakly adsorbed onto xylan, allowing some degree of free movement. Consequently, end-wise polymerization proceeds more slowly than the occurring radical coupling in buffer, exhibiting a polymerization pattern similar to that observed in the dropwise method. Furthermore, steric constraints imposed by the polysaccharide matrix may have suppressed coupling at the C5-position, thereby promoting the formation of β- O -4 linkages.