The mechanism for regeneration of the active site "peroxidatic" cysteine in 1-Cys peroxiredoxins is a matter of debate. Saccharomyces cerevisiae Prx1 is a mitochondrial enzyme belonging to the 1-Cys Prx while Grx2 is involved in antioxidant defense and localizes at the mitochondria, so we hypothesized that it could be a perfect candidate to resolve the sulfenate in Prx1 with GSH. In vitro experiments with purified Prx1p and Grx2p demonstrate that Grx2, at concentrations below 1 microM, coupled to GSH is a very efficient thiolic intermediary for the reduction of the peroxidatic Cys in Prx1. Prx1 forms oligomeric aggregates natively, but depolymerizes down to a dimeric sate upon treatment with GSH. The catalytic cycle involves glutathionylation of dimeric Prx1 and deglutathionylation by Grx2. Dihydrolipoamide, a genuine mitochondrial dithiol, can efficiently substitute for GSH. The activity is highest at alkaline pH consistent with the conditions of active respiring mitochondria and the process is highly specific for 1-Cys Prx since Grx2 is totally inactive with human PRX-I, a typical 2-Cys Prx as opposed to the promiscuity of Trx. Our results suggest that while Trx is the reductant involved in the reduction of peroxides by 2-Cys-Prx, Grx might be the natural resolving partner of 1-Cys Prx through a monothiolic mechanism.
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|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Assay||Construct||Conditions||Strain Background||Reference|