title: Genetics, Transcriptional Profiles, and Catalytic Properties of the UDP-Arabinose Mutase Family from Barley.
abstract: Four members of the UDP-Ara mutase (UAM) gene family from barley have been isolated and characterized, and their map positions on chromosomes 2H, 3H, and 4H have been defined. When the genes are expressed in Escherichia coli, the corresponding HvUAM1, HvUAM2, and HvUAM3 proteins exhibit UAM activity, and the kinetic properties of the enzymes have been determined, including Km, Kcat, and catalytic efficiencies. However, the expressed HvUAM4 protein shows no mutase activity against UDP-Ara or against a broad range of other nucleotide sugars and related molecules. The enzymic data indicate therefore that the HvUAM4 protein may not be a mutase. However, the HvUAM4 gene is transcribed at high levels in all the barley tissues examined, and its transcript abundance is correlated with transcript levels for other genes involved in cell wall biosynthesis. The UDP-l-Arap → UDP-l-Araf reaction, which is essential for the generation of the UDP-Araf substrate for arabinoxylan, arabinogalactan protein, and pectic polysaccharide biosynthesis, is thermodynamically unfavorable and has an equilibrium constant of 0.02. Nevertheless, the incorporation of Araf residues into nascent polysaccharides clearly occurs at biologically appropriate rates. The characterization of the HvUAM genes opens the way for the manipulation of both the amounts and fine structures of heteroxylans in cereals, grasses, and other crop plants, with a view toward enhancing their value in human health and nutrition, and in renewable biofuel production.
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, SA 5064, Australia.|Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH) , AlbaNova University Centre, SE-10691 Stockholm, Sweden.
authors.forename: Yves S Y
authors.initials: YS
authors.lastname: Hsieh
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, SA 5064, Australia.
authors.forename: Qisen
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, SA 5064, Australia.
authors.forename: Kuok
authors.initials: K
authors.lastname: Yap
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, SA 5064, Australia.
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Shirley
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, SA 5064, Australia.
authors.forename: Jelle
authors.initials: J
authors.lastname: Lahnstein
authors.affiliation: Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia , 35 Stirling Highway, Crawley, WA 6009, Australia.
authors.forename: Clark J
authors.initials: CJ
authors.lastname: Nelson
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, SA 5064, Australia.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Burton
authors.affiliation: Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia , 35 Stirling Highway, Crawley, WA 6009, Australia.
authors.forename: A Harvey
authors.initials: AH
authors.lastname: Millar
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, SA 5064, Australia.|Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH) , AlbaNova University Centre, SE-10691 Stockholm, Sweden.
authors.forename: Vincent
authors.initials: V
authors.lastname: Bulone
authors.affiliation: Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food and Wine, University of Adelaide , Waite Campus, Glen Osmond, SA 5064, Australia.
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Fincher
mesh_terms: D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000201:enzymology*; D019751:Intramolecular Transferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014539:Uridine Diphosphate Sugars / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D014539:Uridine Diphosphate Sugars; C040817:uridine diphosphate arabinose; D019751:Intramolecular Transferases