Genome-wide analysis of the UDP-glucose dehydrogenase gene family in Arabidopsis, a key enzyme for matrix polysaccharides in cell walls.
Arabidopsis cell walls contain large amounts of pectins and hemicelluloses, which are predominantly synthesized via the common precursor UDP-glucuronic acid. The major enzyme for the formation of this nucleotide-sugar is UDP-glucose dehydrogenase, catalysing the irreversible oxidation of UDP-glucose into UDP-glucuronic acid. Four functional gene family members and one pseudogene are present in the Arabidopsis genome, and they show distinct tissue-specific expression patterns during plant development. The analyses of reporter gene lines indicate gene expression of UDP-glucose dehydrogenases in growing tissues. The biochemical characterization of the different isoforms shows equal affinities for the cofactor NAD(+) ( approximately 40 microM) but variable affinities for the substrate UDP-glucose (120-335 microM) and different catalytic constants, suggesting a regulatory role for the different isoforms in carbon partitioning between cell wall formation and sucrose synthesis as the second major UDP-glucose-consuming pathway. UDP-glucose dehydrogenase is feedback inhibited by UDP-xylose. The relatively (compared with a soybean UDP-glucose dehydrogenase) low affinity of the enzymes for the substrate UDP-glucose is paralleled by the weak inhibition of the enzymes by UDP-xylose. The four Arabidopsis UDP-glucose dehydrogenase isoforms oxidize only UDP-glucose as a substrate. Nucleotide-sugars, which are converted by similar enzymes in bacteria, are not accepted as substrates for the Arabidopsis enzymes.
University of Frankfurt, Plant Molecular Biology, Biocenter, D-60439 Frankfurt, Germany.
Michaela
M
Klinghammer
Raimund
R
Tenhaken
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D005810:Multigene Family; D010802:Phylogeny; D030821:Plants, Genetically Modified; D011134:Polysaccharides / Q000378:metabolism*; D020033:Protein Isoforms; D014533:Uridine Diphosphate Glucose Dehydrogenase / Q000235:genetics* / Q000378:metabolism*
D029681:Arabidopsis Proteins; D011134:Polysaccharides; D020033:Protein Isoforms; D014533:Uridine Diphosphate Glucose Dehydrogenase