Regulation of serine biosynthesis in Arabidopsis. Crucial role of plastidic 3-phosphoglycerate dehydrogenase in non-photosynthetic tissues.
In plants, Ser is synthesized through a couple of pathways. 3-Phosphoglycerate dehydrogenase (PGDH), the first enzyme that is involved in the phosphorylated pathway of Ser biosynthesis, is responsible for the oxidation of 3-phosphoglycerate to phosphohydroxypyruvate. Here we report the first molecular cloning and characterization of PGDH from Arabidopsis thaliana. Sequence analysis of cDNA and a genomic clone revealed that the PGDH gene is composed of three exons, encoding a 623-amino acid polypeptide (66, 453 Da). The deduced protein, containing three of the most conserved regions in the NAD-dependent 2-hydroxyacid dehydrogenase family, has 38-39% identity to its animal and bacterial counterparts. The presence of an N-terminal signal sequence for translocation into plastids was confirmed by particle-gun bombardment experiments using green fluorescence protein as a reporter protein for subcellular localization. Southern hybridization analysis and restriction fragment length polymorphism mapping indicated that PGDH is a single-copy gene that is mapped to the upper arm of chromosome 1. Northern hybridization analysis indicated preferential expression of PGDH mRNA in root tissues of light-grown plants, suggesting that the phosphorylated pathway of Ser biosynthesis plays an important role in supplying Ser to non-photosynthetic tissues. The recombinant enzyme overproduced in Escherichia coli displayed hyperbolic kinetics with respect to 3-phosphoglycerate and NAD+.
Ho
C L
CL
Laboratory of Molecular Biology and Biotechnology, Research Center of Medicinal Resources, Faculty of Pharmaceutical Sciences, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan.
Noji
M
M
Saito
M
M
Saito
K
K
D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology / Q000378:metabolism*; D001412:Bacillus subtilis / Q000201:enzymology; D001483:Base Sequence; D002237:Carbohydrate Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000201:enzymology; D018744:DNA, Plant; D004926:Escherichia coli / Q000235:genetics; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D050543:Phosphoglycerate Dehydrogenase; D010788:Photosynthesis; D018517:Plant Roots / Q000201:enzymology; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000096:biosynthesis*
D018744:DNA, Plant; D012694:Serine; D002237:Carbohydrate Dehydrogenases; D050543:Phosphoglycerate Dehydrogenase