5-Hydroxyconiferyl Aldehyde Modulates Enzymatic Methylation for Syringyl Monolignol Formation, a New View of Monolignol Biosynthesis in Angiosperms*

@article{Li20005HydroxyconiferylAM,
  title={5-Hydroxyconiferyl Aldehyde Modulates Enzymatic Methylation for Syringyl Monolignol Formation, a New View of Monolignol Biosynthesis in Angiosperms*},
  author={Liangbi Li and Jacqueline L. Popko and Toshiaki Umezawa and Vincent L. Chiang},
  journal={The Journal of Biological Chemistry},
  year={2000},
  volume={275},
  pages={6537 - 6545}
}
S-Adenosyl-l-methionine-dependent caffeate O-methyltransferase (COMT, EC 2.1.1.6) has traditionally been thought to catalyze the methylation of caffeate and 5- hydroxyferulate for the biosynthesis of syringyl monolignol, a lignin constituent of angiosperm wood that enables efficient lignin degradation for cellulose production. However, recent recognition that coniferyl aldehyde prevents 5-hydroxyferulate biosynthesis in lignifying tissue, and that the hydroxylated form of coniferyl aldehyde, 5… Expand
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TLDR
Results indicate that COMT may have more than one role in phenylpropanoid metabolism (but probably not in alfalfa), and that engineered COMT enzymes could be useful for metabolic engineering of both lignin and benzaldehyde-derived flavors and fragrances. Expand
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TLDR
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Substrate preferences of O-methyltransferases in alfalfa suggest new pathways for 3-O-methylation of monolignols.
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TLDR
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Engineering Monolignol 4-O-Methyltransferases to Modulate Lignin Biosynthesis*
TLDR
The 4-O-methoxylation of monolignol efficiently impairs oxidative radical coupling in vitro, highlighting the potential for applying this novel enzyme in managing lignin polymerization in planta. Expand
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TLDR
Cloned cDNAs encoding a cytochrome P450 monooxygenase and a caffeate O-methyltransferase from sweetgum and COMT converted coniferyl aldehyde to sinapyl alde Hyde, suggesting a CAld5H/COMT-mediated pathway from guaiacyl to syringyl monolignol biosynthesis via conifldehyde that contrasts with the generally accepted route to Sinapate via ferulate. Expand
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TLDR
The results support the notion that AEOMT represents a novel SAM-dependent OMT, with both CAOMT and CCoAOMT activities and thus the potential to mediate a dual methylation pathway in lignin biosynthesis in loblolly pine xylem. Expand
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Close examination and comparison to a commercially available polyphenol oxidase suggest that the enzyme activities purified from both Lithospermum and sweet potato are polyphenl oxidases rather than specific enzymes of secondary metabolism. Expand
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TLDR
Results indicate that CCoAOMT is associated with lignification during xylogenesis both in vitro and in the plant, whereas COMT is only involved in a stress response in vitro. Expand
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Abstract An O -methyltransferase which catalyzes the formation of the methoxyl groups of guaiacyl lignin was extracted from Japanese black pine seedlings. The enzyme was purified 90-fold by ammoniumExpand
Evidence for a novel biosynthetic pathway that regulates the ratio of syringyl to guaiacyl residues in lignin in the differentiating xylem of Magnolia kobus DC
Abstract. The biosynthetic pathways to monolignols in Magnolia kobus were investigated by feeding stems with a deuterium-labeled precursor. Pentadeutero [γ,γ-2H2, OC2H3] coniferyl alcohol wasExpand
Dual Methylation Pathways in Lignin Biosynthesis
TLDR
Results unequivocally demonstrate that methylation reactions in lignin biosynthesis are catalyzed by both CCoAOMT and CAOMT. Expand
Characterization and site-directed mutagenesis of aspen lignin-specific O-methyltransferase expressed in Escherichia coli.
TLDR
It was concluded that thiol(s) were not important in the catalytic mechanism of this class of O-methyltransferases and sensitivity to the large thiol inhibitor was probably due to reaction of cysteine thiol near the surface which sterically hindered the active site. Expand
Differential Expression of Two O-Methyltransferases in Lignin Biosynthesis in Zinnia elegans
TLDR
The results indicate that the expression of these two O-methyltransferases is differentially regulated during lignification in different cell types in Zinnia, and suggest that all the intermediates in the CAOMT-mediated methylation pathway might become substrates for the CCoAOMt-mediatedmethylation pathway after coenzyme A ligation when these two pathways occur in the same lignifying cell types. Expand
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