The function of Ensembl gene identifier ENSG00000174156 (GSTA3, glutathione S-transferase alpha 3) is as follows. Conjugation of reduced glutathione to a wide number of exogenous and endogenous hydrophobic electrophiles. Catalyzes isomerization reactions that contribute to the biosynthesis of steroid hormones. Efficiently catalyze obligatory double-bond isomerizations of delta(5)-androstene-3,17-dione and delta(5)-pregnene-3,20-dione, precursors to testosterone and progesterone, respectively. Has substantial activity toward aflatoxin B1-8,9-epoxide (By similarity). {ECO:0000250|UniProtKB:P30115, ECO:0000269|PubMed:11418619, ECO:0000269|PubMed:15595823, ECO:0000269|PubMed:20083122}.