GSTA3 (glutathione S-transferase alpha 3) is a cytosolic enzyme with dual catalytic functions. Primarily, it conjugates reduced glutathione to hydrophobic electrophiles as part of xenobiotic detoxification 1. Additionally, GSTA3-3 is the most catalytically efficient steroid isomerase in humans, converting Δ5-androstene-3,17-dione to testosterone and Δ5-pregnene-3,20-dione to progesterone precursors with ten-fold greater efficiency than GSTA1-1 2. The enzyme catalyzes these reactions through Tyr9 and Arg15 residues that facilitate glutathione deprotonation 2. GSTA3 plays a protective role against oxidative stress-mediated pathologies. In renal fibrosis, GSTA3 attenuates tubular epithelial-mesenchymal transition by reducing reactive oxygen species production; its downregulation correlates with disease progression 3. This protective mechanism operates through the PI3K–Keap1/Nrf2–GSTA3 signaling pathway 4. In non-alcoholic steatohepatitis, hepatic GSTA3 expression increases with elevated NADPH levels, reducing lipid peroxidation and inflammation in female mice 5. Clinically, GSTA3 shows significant disease associations. Reduced GSTA3 expression is a poor prognostic factor in gastric cancer (P=3.4×10⁻⁶) 6, and GSTA3 appears as a diagnostic biomarker in Alzheimer's disease and mild cognitive impairment panels 7. GSTA3 also represents a crosstalk gene between psoriasis and IgA nephropathy 8, suggesting broader inflammatory disease involvement.