Journal Article

Genome-wide analysis of the UDP-glucose dehydrogenase gene family in <i>Arabidopsis</i>, a key enzyme for matrix polysaccharides in cell walls

Michaela Klinghammer and Raimund Tenhaken

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 13, pages 3609-3621
Published in print October 2007 | ISSN: 0022-0957
Published online October 2007 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/erm209

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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+ (∼40 μM) but variable affinities for the substrate UDP-glucose (120–335 μM) 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.

Keywords: Cell wall precursor; gene expression; hemicellulose; nucleotide-sugar; UDP-glucose dehydrogenase

Journal Article.  6852 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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