Glutathione S-transferase-like protein; part of the gene cluster that mediates the biosynthesis of the bibenzoquinone oosporein, a metabolite required for fungal virulence that acts by evading host immunity to facilitate fungal multiplication in insects (PubMed:26305932). The non-reducing polyketide synthase OpS1 produces orsellinic acid by condensing acetyl-CoA with 3 malonyl-CoA units (PubMed:26305932). Orsellinic acid is then hydroxylated to benzenetriol by the hydroxylase OpS4 (PubMed:26305932). The intermediate is oxidized either nonenzymatically to 5,5'-dideoxy-oosporein or enzymatically to benzenetetrol by the oxidoreductase OpS7 (PubMed:26305932). The latter is further dimerized to oosporein by the catalase OpS5 (PubMed:26305932). OpS6 probably functions en route for protecting cells against oxidative stress by scavenging any leaked free radical form of benzenetetrol by activating the thiol group of glutathione (PubMed:26305932). Secondary metabolite biosynthesis. Expression is positively regulated by the oosporein cluster specific regulator OpS3 that binds the promoter at a 5'-CGGA-3' motif (PubMed:26305932). Expression is negatively regulated by the global transcription factor Msn2 that binds the stress-response element 5'-AGGGG-3' (PubMed:26305932). Does not impair the production of oosporein (PubMed:26305932). Belongs to the GST superfamily.