title: Molecular characterization of quinate and shikimate metabolism in Populus trichocarpa.
abstract: The shikimate pathway leads to the biosynthesis of aromatic amino acids essential for protein biosynthesis and the production of a wide array of plant secondary metabolites. Among them, quinate is an astringent feeding deterrent that can be formed in a single step reaction from 3-dehydroquinate catalyzed by quinate dehydrogenase (QDH). 3-Dehydroquinate is also the substrate for shikimate biosynthesis through the sequential actions of dehydroquinate dehydratase (DQD) and shikimate dehydrogenase (SDH) contained in a single protein in plants. The reaction mechanism of QDH resembles that of SDH. The poplar genome encodes five DQD/SDH-like genes (Poptr1 to Poptr5), which have diverged into two distinct groups based on sequence analysis and protein structure prediction. In vitro biochemical assays proved that Poptr1 and -5 are true DQD/SDHs, whereas Poptr2 and -3 instead have QDH activity with only residual DQD/SDH activity. Poplar DQD/SDHs have distinct expression profiles suggesting separate roles in protein and lignin biosynthesis. Also, the QDH genes are differentially expressed. In summary, quinate (secondary metabolism) and shikimate (primary metabolism) metabolic activities are encoded by distinct members of the same gene family, each having different physiological functions.
authors.affiliation: From the Department of Biology and Centre for Forest Biology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada.
authors.forename: Jia
authors.initials: J
authors.lastname: Guo
authors.affiliation: From the Department of Biology and Centre for Forest Biology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada.
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Carrington
authors.affiliation: From the Department of Biology and Centre for Forest Biology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada.
authors.forename: Annette
authors.initials: A
authors.lastname: Alber
authors.affiliation: From the Department of Biology and Centre for Forest Biology, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada je@uvic.ca.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Ehlting
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D020869:Gene Expression Profiling; D017343:Genes, Plant; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D032107:Populus / Q000235:genetics / Q000378:metabolism*; D011801:Quinic Acid / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012765:Shikimic Acid / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D011801:Quinic Acid; D012765:Shikimic Acid; D000429:Alcohol Oxidoreductases; C022511:quinate dehydrogenase; C022641:Shikimate dehydrogenase
keywords: Enzyme Kinetics; Gene Expression; Plant Biochemistry; Plant Defense; Primary Metabolism; Quinate Biosynthesis; Secondary Metabolism; Shikimate Pathway