Skip to Main content Skip to Navigation
Theses

Etude du métabolisme des phénylpropanoïdes; analyse de l'interaction de la caféoyl-coenzyme A 3-O-méthyltransférase (CCoAOMT) avec son substrat et caractérisation fonctionnelle d'une nouvelle acyltransférase, l'HydroxyCinnamoyl-CoA : shikimate/quinate hydroxycinnamoyl Transférase (HCT).

Abstract : I have studied two enzymes involved in phenylpropanoid metabolism in plants. The phenylpropanoid pathway leads from phenylalanine, to a large array of compounds involved in the development and interactions with the environment. Among these products are flower pigments, antibiotics (termed phytoalexins) that accumulate in diseased plants, signals implicated in the recognition of microbes, UV irradiation protectants, and the building units of lignin. Lignin is an essential component of wood that provides rigidity to cell walls and impermeability to vascular tissues. It is a three-dimensional polymer comprising three units having in common the same aromatic ring but differing in their degree of methylation and hydroxylation. Caffeoyl-coenzyme A O-methyltransferase (CCoAOMT) is the first of the two O-methyltransferase involved in lignin biosynthesis. This enzyme uses specifically CoA-esters as substrates. My initial work was to characterize the active site of CCoAOMT taking avantage of the fact that animal catechol O-methyltransferases and plant CCoAOMT share about 20% amino acid sequence identity and display common structural features. The crystallographic structure of rat liver catechol O-methyltransferase was used as a template to construct a homology model for tobacco CCoAOMT. Integrating site-directed mutagenesis and substrate specificity data, the three-dimensional model identified several amino acid residues involved in CoA-esters binding. I also characterized a new acyltransferase named hydroxycinnamoyl-CoA: shikimate/quinate hydroxycinnamoyltransferase (HCT) involved in phenylpropanoid metabolism. HCT belongs to a plant acyltransferase gene family, the members of which have various functions. In vitro, HCT catalyzed the synthesis of shikimate and quinate esters, shown to be substrates of the cytochrome P450 3-hydroxylase. Finally, I confirmed by spatio temporal analyses and virus-induced gene silencing approach the involvement of HCT in lignin biosynthesis.
Complete list of metadata

https://tel.archives-ouvertes.fr/tel-00003598
Contributor : Laurent Hoffmann <>
Submitted on : Friday, October 17, 2003 - 4:32:47 PM
Last modification on : Friday, August 23, 2019 - 1:17:33 AM
Long-term archiving on: : Friday, April 2, 2010 - 6:57:01 PM

Identifiers

  • HAL Id : tel-00003598, version 1

Collections

Citation

Laurent Hoffmann. Etude du métabolisme des phénylpropanoïdes; analyse de l'interaction de la caféoyl-coenzyme A 3-O-méthyltransférase (CCoAOMT) avec son substrat et caractérisation fonctionnelle d'une nouvelle acyltransférase, l'HydroxyCinnamoyl-CoA : shikimate/quinate hydroxycinnamoyl Transférase (HCT).. Biologie cellulaire. Université Louis Pasteur - Strasbourg I, 2003. Français. ⟨tel-00003598⟩

Share

Metrics

Record views

910

Files downloads

18716