title: Expression of a glutamate decarboxylase homologue is required for normal oxidative stress tolerance in Saccharomyces cerevisiae.
abstract: The action of gamma-aminobutyrate (GABA) as an intercellular signaling molecule has been intensively studied, but the role of this amino acid metabolite in intracellular metabolism is poorly understood. In this work, we identify a Saccharomyces cerevisiae homologue of the GABA-producing enzyme glutamate decarboxylase (GAD) that is required for normal oxidative stress tolerance. A high copy number plasmid bearing the glutamate decarboxylase gene (GAD1) increases resistance to two different oxidants, H(2)O(2) and diamide, in cells that contain an intact glutamate catabolic pathway. Structural similarity of the S. cerevisiae GAD to previously studied plant enzymes was demonstrated by the cross-reaction of the yeast enzyme to a antiserum directed against the plant GAD. The yeast GAD also bound to calmodulin as did the plant enzyme, suggesting a conservation of calcium regulation of this protein. Loss of either gene encoding the downstream steps in the conversion of glutamate to succinate reduced oxidative stress tolerance in normal cells and was epistatic to high copy number GAD1. The gene encoding succinate semialdehyde dehydrogenase (UGA5) was identified and found to be induced by H(2)O(2) exposure. Together, these data strongly suggest that increases in activity of the glutamate catabolic pathway can act to buffer redox changes in the cell.
authors.affiliation: Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: S T
authors.initials: ST
authors.lastname: Coleman
authors.forename: T K
authors.initials: TK
authors.lastname: Fang
authors.forename: S A
authors.initials: SA
authors.lastname: Rovinsky
authors.forename: F J
authors.initials: FJ
authors.lastname: Turano
authors.forename: W S
authors.initials: WS
authors.lastname: Moye-Rowley
mesh_terms: D000595:Amino Acid Sequence; D002147:Calmodulin / Q000378:metabolism; D003001:Cloning, Molecular; D003958:Diamide / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D018628:Gene Dosage; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal / Q000235:genetics; D005968:Glutamate Decarboxylase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006884:Hydroxybutyrate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress; D011485:Protein Binding; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D016877:Oxidants; D011993:Recombinant Fusion Proteins; D003958:Diamide; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D006861:Hydrogen Peroxide; C026839:succinate semialdehyde reductase; D006884:Hydroxybutyrate Dehydrogenase; D005968:Glutamate Decarboxylase