No abstract

Peroxiredoxins (Prxs) are Cys-based highly efficient peroxidases. Prxs can be classified as 2-Cys and 1-Cys, according to the number of cysteines residues involved in the catalysis. 1-Cys Prx enzymes are still poorly characterized and the identities of their biological reductants are still controversial. Some of the reductant candidates are thioredoxin (Trx) and ascorbate. A. fumigatus is a human pathogen fungus that possesses two 1-Cys Prxs (Prx1 and PrxC). We had shown before that these Prxs display high reactivity towards H 2 O 2 ( $ 107 M-1s-1). Here, we described our studies on the reduction step. Thus, the genes encoding for Trx system from this fungus were cloned, expressed and purified. The 4 Trxs were efficiently reduced by TrxR (kcat/Km $ 106 M-1s-1). However, our preliminary data indicated that Prx1 and PrxC were poorly reduced by these oxidoreductases. We are now investigating the erythroascorbate (a 5-carbon ascorbate analogue) role in Prx reduction. Since erythroascorbate can be found glycosylated in several fungi species, we are trying to identify and quantitate this reducing agent by mass spectrometry. The biochemical characterization of these Prxs catalytic cycle can open new therapeutical strategies, since at least Prx1 is involved in fungus virulence.