title: Biochemical and physiological analyses of NADPH-dependent thioredoxin reductase isozymes in Euglena gracilis.
abstract: At least four peroxiredoxins that are coupled with the thioredoxin (Trx) system have been shown to play a key role in redox metabolism in the unicellular phytoflagellate Euglena gracilis. In order to clarify Trx-mediated redox regulation in this alga, we herein identified three NADPH-dependent thioredoxin reductases (NTRs) using a homologous search and characterized their enzymatic properties and physiological roles. Each Euglena NTR protein belonged to the small, large, and NTRC types, and were named EgNTR1, EgNTR2, and EgNTRC, respectively. EgNTR2 was phylogenetically different from the known NTRs in eukaryotic algae. EgNTR1 was predicted to be localized in mitochondria, EgNTR2 in the cytosol, and EgNTRC in plastids. The catalytic efficiency of EgNTR2 for NADPH was 30-46-fold higher than those of EgNTR1 and truncated form of EgNTRC, suggested that large type EgNTR2 reduced Trx more efficiently. The silencing of EgNTR2 gene expression resulted in significant growth inhibition and cell hypertrophy in Euglena cells. These results suggest that EgNTRs function in each cellular compartment and are physiologically important, particularly in the cytosol.
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Tamaki
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0076, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Maruta
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sawa
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0076, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0076, Japan. Electronic address: ishikawa@life.shimane-u.ac.jp.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
mesh_terms: D020418:Algal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D003600:Cytosol / Q000378:metabolism; D005056:Euglena gracilis / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010802:Phylogeny; D018087:Plastids / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D013880:Thioredoxin-Disulfide Reductase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D020418:Algal Proteins; D015800:Protozoan Proteins; D013880:Thioredoxin-Disulfide Reductase
keywords: Euglena gracilis; NADPH-dependent thioredoxin reductase; Redox regulation; Thioredoxin system