Three Members of the Arabidopsis Glycosyltransferase Family 8 Are Xylan Glucuronosyltransferases

Xylan is a major component of the plant cell wall and the most abundant noncellulosic component in the secondary cell walls that constitute the largest part of plant biomass. Dicot glucuronoxylan consists of a linear backbone of β(1,4)-linked xylose residues substituted with α(1,2)-linked glucuronic...

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Published in:Plant physiology (Bethesda) 2012-08, Vol.159 (4), p.1408-1417
Main Authors: Rennie, Emilie A., Hansen, Sara Fasmer, Baidoo, Edward E.K., Hadi, Masood Z., Keasling, Jay D., Scheller, Henrik Vibe
Format: Article
Language:English
Subjects:
Arabidopsis - enzymology
Arabidopsis Proteins - genetics
Arabidopsis Proteins - isolation & purification
Arabidopsis Proteins - metabolism
BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES
Biological and medical sciences
Biosynthesis
Cell walls
Electrostatics
Enzymes
Fundamental and applied biological sciences. Psychology
Glucuronosyltransferase - metabolism
Glycosyltransferases - metabolism
Microsomes
Microsomes - enzymology
Models, Molecular
Molecules
Nicotiana - metabolism
Phylogeny
Plant cells
Plant physiology and development
Plants
Protein Transport
Proteins
Recombinant Proteins - isolation & purification
Recombinant Proteins - metabolism
Subcellular Fractions - enzymology
Xylans
Xylans - metabolism
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Summary:Xylan is a major component of the plant cell wall and the most abundant noncellulosic component in the secondary cell walls that constitute the largest part of plant biomass. Dicot glucuronoxylan consists of a linear backbone of β(1,4)-linked xylose residues substituted with α(1,2)-linked glucuronic acid (GlcA). Although several genes have been implicated in xylan synthesis through mutant analyses, the biochemical mechanisms responsible for synthesizing xylan are largely unknown. Here, we show evidence for biochemical activity of GUX1 (for GlcA substitution of xylan 1), a member of Glycosyltransferase Family 8 in Arabidopsis (Arabidopsis thaliana) that is responsible for adding the glucuronosyl substitutions onto the xylan backbone. GUX1 has characteristics typical of Golgi-localized glycosyltransferases and a K m for UDP-GlcA of 165 μM. GUX1 strongly favors xylohexaose as an acceptor over shorter xylooligosaccharides, and with xylohexaose as an acceptor, GlcA is almost exclusively added to the fifth xylose residue from the nonreducing end. We also show that several related proteins, GUX2 to GUX5 and Plant Glycogenin-like Starch Initiation Protein6, are Golgi localized and that only two of these proteins, GUX2 and GUX4, have activity as xylan α-glucuronosyltransferases.
ISSN:0032-0889
1532-2548
1532-2548
DOI:10.1104/pp.112.200964