title: Serine racemases from barley, Hordeum vulgare L., and other plant species represent a distinct eukaryotic group: gene cloning and recombinant protein characterization.
abstract: Several d-amino acids have been identified in plants. However, the biosynthetic pathway to them is unclear. In this study, we cloned and sequenced a cDNA encoding a serine racemase from barley which contained an open reading frame encoding 337 amino acid residues. The deduced amino acid sequence showed significant identity to plant and mammalian serine racemases and contained conserved pyridoxal 5-phosphate (PLP)-binding lysine and PLP-interacting amino acid residues. The purified gene product catalyzed not only racemization of serine but also dehydration of serine to pyruvate. The enzyme requires PLP and divalent cations such as Ca(2+), Mg(2+), or Mn(2+), but not ATP, whereas mammalian serine racemase activity is increased by ATP. In addition to the results regarding the effect of ATP on enzyme activity and the phylogenetic analysis of eukaryotic serine racemases, the antiserum against Arabidopsis serine racemase did not form a precipitate with barley and rice serine racemases. This suggests that plant serine racemases represent a distinct group in the eukaryotic serine racemase family and can be clustered into monocot and dicot types.
authors.affiliation: Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fujitani
authors.forename: Terumi
authors.initials: T
authors.lastname: Horiuchi
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Ito
authors.forename: Manabu
authors.initials: M
authors.lastname: Sugimoto
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D002412:Cations / Q000378:metabolism; D003001:Cloning, Molecular; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D019998:Racemases and Epimerases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D000099300:Serine Racemase
chemical_list: D000255:Adenosine Triphosphate; D002412:Cations; D010940:Plant Proteins; D019998:Racemases and Epimerases; D000099300:Serine Racemase