Characterization and functional analysis of a recombinant tau class glutathione transferase GmGSTU2-2 from Glycine max.

The plant tau class glutathione transferases (GSTs) perform diverse catalytic as well as non-catalytic roles in detoxification of xenobiotics, prevention of oxidative damage and endogenous metabolism. In the present work, the tau class isoenzyme GSTU2-2 from Glycine max (GmGSTU2-2) was characterized. Gene expression analysis of GmGSTU2 suggested a highly specific and selective induction pattern to osmotic stresses, indicating that gene expression is controlled by a specific mechanism. Purified, recombinant GmGSTU2-2 was shown to exhibit wide-range specificity towards xenobiotic compounds and ligand-binding properties, suggesting that the isoenzyme could provide catalytic flexibility in numerous metabolic conditions. Homology modeling and phylogenetic analysis suggested that the catalytic and ligand binding sites of GmGSTU2-2 are well conserved compared to other tau class GSTs. Structural analysis identified key amino acid residues in the hydrophobic binding site and provided insights into the substrate specificity of this enzyme. The results established that GmGSTU2-2 participates in a broad network of catalytic and regulatory functions involved in the plant stress response.