title: Molecular mechanisms of the resistance to hydrogen peroxide of enzymes involved in the calvin cycle from halotolerant Chlamydomonas sp. W80.
abstract: cDNA clones encoding NADP(+)-glyceraldehyde-3-phosphate dehydrogenase (NADP(+)-GAPDH) and sedoheptulose-1,7-bisphosphatase (SBPase) were isolated and characterized from halotolerant Chlamydomonas sp. W80 (C. W80) cells. The cDNA clone for NADP(+)-GAPDH encoded 369 amino acid residues, preceded by the chloroplast transit peptide (37 amino acid residues). The cDNA clone for SBPase encoded 351 amino acids with the chloroplast transit peptide. The activities of NADP(+)-GAPDH and SBPase from C. W80 cells were resistant to H(2)O(2) up to 1 mM, as distinct from spinach chloroplastic thiol-modulated enzymes. The illumination to the dark-adapted cells and dithiothreitol treatment to the crude homogenate had little effect on the activities of NADP(+)-GAPDH and SBPase in C. W80. Modeling of the tertiary structures of NADP(+)-GAPDH and SBPase suggests that resistance of the enzymes to H(2)O(2) in C. W80 is due to the different conformational structures in the vicinity of the Cys residues of the chloroplastic enzymes between higher plant and C. W80 cells.
authors.affiliation: Department of Food and Nutrition, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tamoi
authors.forename: H
authors.initials: H
authors.lastname: Kanaboshi
authors.forename: H
authors.initials: H
authors.lastname: Miyasaka
authors.forename: S
authors.initials: S
authors.lastname: Shigeoka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002696:Chlamydomonas / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects; D004229:Dithiothreitol / Q000494:pharmacology; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008027:Light; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D006861:Hydrogen Peroxide; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D010744:Phosphoric Monoester Hydrolases; C022627:sedoheptulose-bisphosphatase; D004229:Dithiothreitol