Glutaredoxins (Grxs) are a class of GSH (glutathione)-dependent thiol-disulfide oxidoreductase enzymes. They use the cellular redox buffer GSSG (glutathione disulfide)/GSH directly to catalyze these exchange reactions. Grxs feature dithiol active sites and can shuttle rapidly between three oxidation states, namely dithiol Grx(SH)₂, mixed disulfide Grx(SH)(SSG) and oxidized disulfide Grx(SS). Each is characterized by a distinct standard reduction potential [Formula: see text] The [Formula: see text] values for the redox couple Grx(SS)/Grx(SH)₂ are available, but a recent estimate differs by over 100 mV from the literature values. No estimates are available for [Formula: see text] for the mixed disulfide couple Grx(SH)(SSG)/(Grx(SH)₂ + GSH). This work determined both [Formula: see text] and [Formula: see text] for two representative Grx enzymes, Homo sapiens HsGrx1 and Escherichia coli EcGrx1. The empirical approaches were verified rigorously to overcome the sensitivity of these redox-labile enzymes to experimental conditions. The classic method of acid 'quenching' was demonstrated to shift the thiol-disulfide redox equilibria. Both enzymes exhibit an [Formula: see text] (vs. SHE) at a pH of 7.0. Their [Formula: see text] values (-213 and -230 mV for EcGrx1 and HsGrx1, respectively) are slightly less negative than that ([Formula: see text]) of the redox buffer GSSG/2GSH. Both [Formula: see text] and [Formula: see text] vary with log [GSH], but the former more sensitively by a factor of 2. This confers dual catalytic functions to a Grx enzyme as either an oxidase at low [GSH] or as a reductase at high [GSH]. Consequently, these enzymes can participate efficiently in either glutathionylation or deglutathionylation. The catalysis is demonstrated to proceed via a monothiol ping-pong mechanism relying on a single Cys residue only in the dithiol active site.

EXPLOR_STEP=$WICRI_ROOT/Bois/explor/GlutaredoxinV1/Data/Main/Exploration

HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 000315 | SxmlIndent | more

HfdSelect -h $EXPLOR_AREA/Data/Main/Exploration/biblio.hfd -nk 000315 | SxmlIndent | more

{{Explor lien
   |wiki=    Bois
   |area=    GlutaredoxinV1
   |flux=    Main
   |étape=   Exploration
   |type=    RBID
   |clé=     pubmed:28963348
   |texte=   Reduction potentials of protein disulfides and catalysis of glutathionylation and deglutathionylation by glutaredoxin enzymes.
}}

HfdIndexSelect -h $EXPLOR_AREA/Data/Main/Exploration/RBID.i   -Sk "pubmed:28963348" \
       | HfdSelect -Kh $EXPLOR_AREA/Data/Main/Exploration/biblio.hfd   \
       | NlmPubMed2Wicri -a GlutaredoxinV1