Ferulic acid is bound to the primary cell walls of all gymnosperm families

Abstarct Xyloglucan is the most abundant hemicellulose in the primary cell walls of dicots. Dicot xyloglucan is the XXXG-type consisting of repeating units of three consecutive xylosylated Glc residues followed by one unsubstituted Glc. Its xylosylation is catalyzed by xyloglucan 6-xylosyltransferases (XXTs) and there exist five XXTs (AtXXT1-5) in Arabidopsis. While AtXXT1and AtXXT2 have been shown to add the first two Xyl residues in the XXXG repeat, which XXTs are responsible for the addition of the third Xyl residue remains elusive although AtXXT5 was a proposed candidate. In this report, we generated recombinant proteins of all five Arabidopsis XXTs and one rice XXT (OsXXT1) in the mammalian HEK293 cells and investigated their ability to sequentially xylosylate Glc residues to generate the XXXG xylosylation pattern. We found that like AtXXT1/2, AtXXT4 and OsXXT1 could efficiently xylosylate the cellohexaose (G6) acceptor to produce mono- and di-xylosylated G6, whereas AtXXT5 was only barely capable of adding one Xyl onto G6. When AtXXT1-catalyzed products were used as acceptors, AtXXT1/2/4 and OsXXT1 but not AtXXT5 were able to xylosylate additional Glc residues to generate tri- and tetra-xylosylated G6. Further characterization of the tri- and tetra-xylosylated G6 revealed that they had the sequence of GXXXGG and GXXXXG with three and four consecutive xylosylated Glc residues, respectively. In addition, we have found that although tri-xylosylation occurred on G6, cello-oligomers with a degree of polymerization of 3 to 5 could only be mono- and di-xylosylated. Together, these results indicate that each of AtXXT1/2/4 and OsXXT1 is capable of sequentially adding Xyl onto three contiguous Glc residues to generate the XXXG xylosylation pattern and these findings provide new insight into the biochemical mechanism underlying xyloglucan biosynthesis.

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The Structural Polymers of the Primary Cell Walls of Dicots

Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products ◽

10.1007/978-3-7091-8545-2_2 ◽

1979 ◽

pp. 191-249 ◽

Cited By ~ 9

Author(s):

M. McNeil ◽

A. G. Darvill ◽

P. Albersheim

Keyword(s):

Cell Walls ◽

Primary Cell ◽

Structural Polymers

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New Products Generated from the Transformations of Ferulic Acid Dilactone

Biomolecules ◽

10.3390/biom10020175 ◽

2020 ◽

Vol 10 (2) ◽

pp. 175 ◽

Cited By ~ 2

Author(s):

Ying He ◽

Yuan Jia ◽

Fachuang Lu

Keyword(s):

Ferulic Acid ◽

Succinic Acid ◽

Plant Cell ◽

Cell Walls ◽

New Products ◽

Plant Cell Walls ◽

Reaction Conditions ◽

Radical Coupling ◽

Naoh Treatment ◽

Derivatives Of

Various ferulic acid (FA) dimers occurring in plant cell walls, such as 8-5-, 8-O-4-, 5-5-, and 8-8-coupled dimers, are effective antioxidants and potential antimicrobials. It is necessary to access these diferulates as reference compounds to validate those isolated from plants. 3,6-bis(4-hydroxy-3-methoxyphenyl)-tetrahydrofuro-[3,4-c]furan-1,4-dione, a 8-8-coupled FA dilactone generated from ferulic acid via radical coupling, has been used to synthesize 8-8-coupled FA dimers although few reports investigated the distribution of products and mechanisms involved in the transformation of FA dilactone. In this work, the FA dilactone, obtained from FA by a peroxidase-catalyzed radical coupling, was reacted under various base/acid conditions. Effects of reaction conditions and workup procedures on the distribution of products were investigated by GC-MS. The isolated products from such treatments of FA dilactone were characterized by NMR. New derivatives of FA dimer including 2-(4-hydroxy-3-methoxybenzylidene)-3-(hydroxyl-(4-hydroxy-3-methoxyphenyl)methyl)succinic acid and 2-(bis(4-hydroxy-3-methoxyphenyl)-methyl)-succinic acid were produced from NaOH treatment. Another novel 8-8-coupled cyclic FA dimer, diethyl 6-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-7-methoxy-1,2-dihydronaphthalene-2,3-dicarboxylate was identified in products from FA dilactone treated by dry HCl in absolute ethanol. Mechanisms involved in such transformations were proposed.

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