Beschreibung:
<jats:p>One of the major sugars present in the plant cell wall is <jats:sc>d</jats:sc>‐galacturonate, the dominant monosaccharide in pectic polysaccharides. Previous work indicated that one of the activated precursors necessary for the synthesis of pectins is UDP‐<jats:sc>d</jats:sc>‐galacturonate, which is synthesized from UDP‐<jats:sc>d</jats:sc>‐glucuronate by a UDP‐<jats:sc>d</jats:sc>‐glucuronate 4‐epimerase (GAE). Here, we report the identification, cloning and characterization of a GAE6 from <jats:italic>Arabidopsis thaliana</jats:italic>. Functional analysis revealed that this enzyme converts UDP‐<jats:sc>d</jats:sc>‐glucuronate to UDP‐<jats:sc>d</jats:sc>‐galacturonate in vitro. An expression analysis of this epimerase and its five homologs in the <jats:italic>Arabidopsis</jats:italic> 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 <jats:italic>A. thaliana</jats:italic>.</jats:p>