Journal
BIOCHEMICAL JOURNAL
Volume 445, Issue -, Pages 337-347Publisher
PORTLAND PRESS LTD
DOI: 10.1042/BJ20120505
Keywords
Arabidopsis thaliana cytosolic isoform I glyceraldehyde-3-phosphate dehydrogenase (AtGapC1); deglutathionylation; glutathionylation; glycolysis; oxidative stress; redox signalling
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Funding
- Ministero dell'Istruzione, dell'Universita e della Ricerca [PRIN2008XB774B-005]
- ANR (Agence Nationale de la Recherche) [08-BLAN-0153 GLUTAPHOTO, ANR-07-JCJC-0121]
- PHC (Partenariats Hubert Curien) Galilee Project
- Ville de Paris by Research in Paris fellowship
- Agence Nationale de la Recherche (ANR) [ANR-07-JCJC-0121] Funding Source: Agence Nationale de la Recherche (ANR)
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Plants contain both cytosolic and chloroplastic GAPDHs (glyceraldehyde-3-phosphate dehydrogenases). In Arabidopsis thaliann, cytosolic GAPDH is involved in the glycolytic pathway and is represented by two differentially expressed isoforms (GapC1 and GapC2) that are 98% identical in amino acid sequence. In the present study we show that GapC1 is a phosphorylating NAD-specific GAPDH with enzymatic activity strictly dependent on Cyst(149). Catalytic Cys(149) is the only solvent-exposed cystine of the protein and its thiol is relatively acidic (pK(a) = 5.7). This property makes GapCl sensitive to oxidation by H2O2, which appears to inhibit enzyme activity by converting the thiolate of Cys(149) (-S-) into irreversible oxidized forms (-SO2- and -SO3-) via a labile sulfenate intermediate (-SO-). GSH (reduced glutathione) prevents this irreversible process by reacting with Cys(149) sulfenates to give rise to a mixed disulfide (Cys(149)-SSG), as demonstrated by both MS and biotinylated GSH. Glutathionylated GapC1 can be fully reactivated either by cytosolic glutaredoxin, via a GSHdependent monothiol mechanism, or, less efficiently, by cytosolic thioredoxins physiologically reduced by NADPH:thioredoxin reductase. The potential relevance of these findings is discussed in the light of the multiple functions of GAPDH in eukaryotic cells (e.g. glycolysis, control of gene expression and apoptosis) that appear to be influenced by the redox state of the catalytic cys(149).
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