Biochemical Characterization of Glutaredoxins from Chlamydomonas reinhardtii Reveals the Unique Properties of a Chloroplastic CGFS-type Glutaredoxin

Glutaredoxins (GRXs) are small ubiquitous disulfide oxidoreductases known to use GSH as electron donor. In photosynthetic organisms, little is known about the biochemical properties of GRXs despite the existence of ∼30 different isoforms in higher plants. We report here the biochemical characterizat...

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Bibliographic Details
Published in:The Journal of biological chemistry 2008-04, Vol.283 (14), p.8868-8876
Main Authors: Zaffagnini, Mirko, Michelet, Laure, Massot, Vincent, Trost, Paolo, Lemaire, Stéphane D.
Format: Article
Language:English
Subjects:
Algal Proteins - chemistry
Algal Proteins - metabolism
Animals
Chlamydomonas
Chlamydomonas reinhardtii
Chlamydomonas reinhardtii - enzymology
Chloroplasts - enzymology
Cytoplasm - enzymology
Ferredoxins - chemistry
Ferredoxins - metabolism
Glutaredoxins - chemistry
Glutaredoxins - metabolism
Glutathione - chemistry
Glutathione - metabolism
Hydrogen-Ion Concentration
Iron-Sulfur Proteins - chemistry
Iron-Sulfur Proteins - metabolism
Isoenzymes - chemistry
Isoenzymes - metabolism
Oxidation-Reduction
Oxidoreductases - chemistry
Oxidoreductases - metabolism
Protozoan Proteins - chemistry
Protozoan Proteins - metabolism
Substrate Specificity
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Summary:Glutaredoxins (GRXs) are small ubiquitous disulfide oxidoreductases known to use GSH as electron donor. In photosynthetic organisms, little is known about the biochemical properties of GRXs despite the existence of ∼30 different isoforms in higher plants. We report here the biochemical characterization of Chlamydomonas GRX1 and GRX3, the major cytosolic and chloroplastic isoforms, respectively. Glutaredoxins are classified on the basis of the amino acid sequence of the active site. GRX1 is a typical CPYC-type GRX, which is reduced by GSH and exhibits disulfide reductase, dehydroascorbate reductase, and deglutathionylation activities. In contrast, GRX3 exhibits unique properties. This chloroplastic CGFS-type GRX is not reduced by GSH and has an atypically low redox potential (–323 ± 4 mV at pH 7.9). Remarkably, GRX3 can be reduced in the light by photoreduced ferredoxin and ferredoxin-thioredoxin reductase. Both GRXs proved to be very efficient catalysts of A4-glyceraldehyde-3-phosphate dehydrogenase deglutathionylation, whereas cytosolic and chloroplastic thioredoxins were inefficient. Glutathionylated A4-glyceraldehyde-3-phosphate dehydrogenase is the first physiological substrate identified for a CGFS-type GRX.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M709567200