title: Phylobiochemical characterization of class-Ib aspartate/prephenate aminotransferases reveals evolution of the plant arogenate phenylalanine pathway.
abstract: The aromatic amino acid Phe is required for protein synthesis and serves as the precursor of abundant phenylpropanoid plant natural products. While Phe is synthesized from prephenate exclusively via a phenylpyruvate intermediate in model microbes, the alternative pathway via arogenate is predominant in plant Phe biosynthesis. However, the molecular and biochemical evolution of the plant arogenate pathway is currently unknown. Here, we conducted phylogenetically informed biochemical characterization of prephenate aminotransferases (PPA-ATs) that belong to class-Ib aspartate aminotransferases (AspAT Ibs) and catalyze the first committed step of the arogenate pathway in plants. Plant PPA-ATs and succeeding arogenate dehydratases (ADTs) were found to be most closely related to homologs from Chlorobi/Bacteroidetes bacteria. The Chlorobium tepidum PPA-AT and ADT homologs indeed efficiently converted prephenate and arogenate into arogenate and Phe, respectively. A subset of AspAT Ib enzymes exhibiting PPA-AT activity was further identified from both Plantae and prokaryotes and, together with site-directed mutagenesis, showed that Thr-84 and Lys-169 play key roles in specific recognition of dicarboxylic keto (prephenate) and amino (aspartate) acid substrates. The results suggest that, along with ADT, a gene encoding prephenate-specific PPA-AT was transferred from a Chlorobi/Bacteroidetes ancestor to a eukaryotic ancestor of Plantae, allowing efficient Phe and phenylpropanoid production via arogenate in plants today.
authors: Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin 53706.
authors: Camilla
authors: C
authors: Dornfeld
authors: Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061.
authors: Alexandra J
authors: AJ
authors: Weisberg
authors: Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061.
authors: Ritesh
authors: R
authors: K C
authors: Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
authors: Natalia
authors: N
authors: Dudareva
authors: Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061.
authors: John G
authors: JG
authors: Jelesko
authors: Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin 53706 maeda2@wisc.edu.
authors: Hiroshi A
authors: http://orcid.org/0000-0003-0246-694X
authors: HA
authors: Maeda
mesh_terms: D000595:Amino Acid Sequence; D000600:Amino Acids, Dicarboxylic / Q000378:metabolism; D001219:Aspartate Aminotransferases / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D053898:Biosynthetic Pathways; D041883:Chlorobium / Q000201:enzymology / Q000235:genetics; D017124:Conserved Sequence; D053138:Cyclohexenes / Q000378:metabolism; D019143:Evolution, Molecular; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010649:Phenylalanine / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D010944:Plants / Q000201:enzymology* / Q000235:genetics; D016415:Sequence Alignment; D000637:Transaminases / Q000235:genetics* / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D000600:Amino Acids, Dicarboxylic; D001426:Bacterial Proteins; D053138:Cyclohexenes; D010940:Plant Proteins; D014443:Tyrosine; D010649:Phenylalanine; C015478:pretyrosine; D000637:Transaminases; C044954:prephenate aminotransferase; D001219:Aspartate Aminotransferases; D006836:Hydro-Lyases; C022437:pretyrosine dehydratase