SULT1E1 encodes a cytosolic sulfotransferase that catalyzes the sulfate conjugation of estrogens using 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as a sulfonate donor 1. This enzyme has the highest affinity for estradiol and estrone among the 10 known human sulfotransferase isoforms, making it a key regulator of estrogen homeostasis through estrogen inactivation 1. The enzyme functions by transferring sulfate groups to hydroxyl moieties on steroid substrates, particularly estrogens, leading to their metabolic inactivation and facilitating excretion 2. SULT1E1 demonstrates significant genetic polymorphism, with at least three functionally significant nonsynonymous variants (Asp22Tyr, Ala32Val, Pro253His) that alter enzyme kinetics and protein levels 1. These polymorphisms result in differential sulfating activities toward estradiol and drug compounds like 4-hydroxytamoxifen and diethylstilbestrol, potentially affecting individual drug metabolism 2. Clinically, SULT1E1 expression correlates with disease progression and prognosis in multiple cancers. In lung adenocarcinoma, reduced SULT1E1 expression associates with advanced TNM stage and shorter overall survival 3. In high-grade meningiomas, a unique SULT1E1-positive cell subpopulation promotes tumor aggressiveness and recurrence by modulating macrophage polarization 4. The enzyme also participates in ovulation-related processes, with its expression being regulated during reproductive cycles 5.