title: Identification and characterization of a UDP-D-glucuronate 4-epimerase in Arabidopsis.
abstract: One of the major sugars present in the plant cell wall is d-galacturonate, the dominant monosaccharide in pectic polysaccharides. Previous work indicated that one of the activated precursors necessary for the synthesis of pectins is UDP-d-galacturonate, which is synthesized from UDP-d-glucuronate by a UDP-d-glucuronate 4-epimerase (GAE). Here, we report the identification, cloning and characterization of a GAE6 from Arabidopsis thaliana. Functional analysis revealed that this enzyme converts UDP-d-glucuronate to UDP-d-galacturonate in vitro. An expression analysis of this epimerase and its five homologs in the Arabidopsis genome by quantitative RT-PCR and promoter::GUS fusions indicated differential expression of the family members in plant tissues and expression of all isoforms in the developing pollen of A. thaliana.
authors.affiliation: Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Golm, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Usadel
authors.forename: Urte
authors.initials: U
authors.lastname: Schlüter
authors.forename: Michael
authors.initials: M
authors.lastname: Mølhøj
authors.forename: Martijn
authors.initials: M
authors.lastname: Gipmans
authors.forename: Rajeev
authors.initials: R
authors.lastname: Verma
authors.forename: Jens
authors.initials: J
authors.lastname: Kossmann
authors.forename: Wolf-Dieter
authors.initials: WD
authors.lastname: Reiter
authors.forename: Markus
authors.initials: M
authors.lastname: Pauly
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001483:Base Sequence; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017931:DNA Primers; D035264:Flowers / Q000201:enzymology; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology; D018517:Plant Roots / Q000201:enzymology; D018547:Plant Stems / Q000201:enzymology; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D011993:Recombinant Fusion Proteins; D002238:Carbohydrate Epimerases; C023258:UDPglucuronate 4-epimerase