Trametes versicolor glutathione transferase Xi 3, a dual Cys‐GST with catalytic specificities of both Xi and Omega classes

Abstract

Glutathione transferases (GSTs) from the Xi and Omega classes have a catalytic cysteine residue, which gives them reductase activities. Until now, they have been assigned distinct substrates. While Xi GSTs specifically reduce glutathionyl-(hydro)quinones, Omega GSTs are specialized in the reduction of glutathionyl-acetophenones. Here, we present the biochemical and structural analysis of TvGSTX1 and TvGSTX3 isoforms from the wood-degrading fungus Trametes versicolor. TvGSTX1 reduces GS-menadione as expected, while TvGSTX3 reduces both Xi and Omega substrates. An in-depth structural analysis indicates a broader active site for TvGSTX3 due to specific differences in the nature of the residues situated in the C-terminal helix α9. This feature could explain the catalytic duality of TvGSTX3. Based on phylogenetic analysis, we propose that this duality might exist in saprophytic fungi and ascomycetes.

Structural Characterization of the Xi Class Glutathione Transferase From the Haloalkaliphilic Archaeon Natrialba magadii

“…Similar to GSTOs, Xi class GSTs also contain a cysteine residue in their active site. This feature is also shared by GSTs belonging to other classes: Beta, Lambda, chloride intracellular channels (CLICs), and dehydroascorbate reductases (DHARs; Allocati et al, 2009; Schwartz et al, 2018).…”

Characterization of Xi-class mycothiol S-transferase from Corynebacterium glutamicum and its protective effects in oxidative stress

“…Hereafter, Meux and co-worker believed, on the basis of sequence analysis and biochemical and structural differences from canonical GSTOs, that GHRs of the GSTOIs should be considered as a new class of GSTs, reclassifying them as GSTXs [6]. In summary, the activities associated to GSTXs were: (i) GSH-dependent thiol transferase activity, being attributable to its structural and functional similarity to glutaredoxins (Grxs), but low or lacking activity toward classical GSTs substrate as 1-chloro-2,4-dinitrobenzene (CDNB) [15]. (ii) Catalyses of several reductive reactions in cellular biochemistry, including dehydroascorbate (DHA) and monomethylarsonic acid (MMA) [15].…”

“…In summary, the activities associated to GSTXs were: (i) GSH-dependent thiol transferase activity, being attributable to its structural and functional similarity to glutaredoxins (Grxs), but low or lacking activity toward classical GSTs substrate as 1-chloro-2,4-dinitrobenzene (CDNB) [15]. (ii) Catalyses of several reductive reactions in cellular biochemistry, including dehydroascorbate (DHA) and monomethylarsonic acid (MMA) [15]. As a DHA reductase, GSTXs reduced DHA for ascorbic acid (AA).…”

“…(iii) Specific reduction of S -glutathionyl-(chloro)hydroquinone (GH), and such activity was not detected for the other GSTOs [6]. However, unlike GSTOs, GSTXs did not have the activity of reducing glutathionyl-acetophenones (which was once thought to be specific to GSTOs), although more recently Schwartz et al [15] found that the GSTX3 from the white rot Trametes versicolor (TvGSTX3) had glutathionyl-acetophenone and GH reductase activities. That is to say that TvGSTX3 reduced both Xi and Omega substrates [15].…”

“…However, unlike GSTOs, GSTXs did not have the activity of reducing glutathionyl-acetophenones (which was once thought to be specific to GSTOs), although more recently Schwartz et al [15] found that the GSTX3 from the white rot Trametes versicolor (TvGSTX3) had glutathionyl-acetophenone and GH reductase activities. That is to say that TvGSTX3 reduced both Xi and Omega substrates [15]. However, nothing was known about the universality and exact molecular mechanism of the catalytic duality of GSTXs.…”