Usadel Björn, Schlüter Urte, Mølhøj Michael, Gipmans Martijn, Verma Rajeev, Kossmann Jens, Reiter Wolf-Dieter, Pauly Markus
Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Golm, Germany.
FEBS Lett. 2004 Jul 2;569(1-3):327-31. doi: 10.1016/j.febslet.2004.06.005.
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.
植物细胞壁中存在的主要糖类之一是D-半乳糖醛酸，它是果胶多糖中的主要单糖。先前的研究表明，果胶合成所需的活化前体之一是UDP-D-半乳糖醛酸，它由UDP-D-葡萄糖醛酸通过UDP-D-葡萄糖醛酸4-表异构酶（GAE）合成。在这里，我们报告了来自拟南芥的GAE6的鉴定、克隆和特性分析。功能分析表明，这种酶在体外将UDP-D-葡萄糖醛酸转化为UDP-D-半乳糖醛酸。通过定量RT-PCR和启动子::GUS融合对该表异构酶及其在拟南芥基因组中的五个同源物进行表达分析，结果表明该家族成员在植物组织中的表达存在差异，并且所有同工型在拟南芥发育中的花粉中均有表达。
