SULT1A1 is a cytosolic sulfotransferase that catalyzes the sulfate conjugation of diverse substrates using PAPS as the sulfonate donor 1. The enzyme displays broad substrate specificity, mediating sulfonation of endogenous molecules including steroid hormones, thyroid hormones, and dopamine, thereby increasing their water solubility and facilitating renal excretion 1. SULT1A1 also conjugates xenobiotics including acetaminophen and analgesics, with genetic polymorphisms significantly affecting drug-sulfation activity 2. A critical dual role involves metabolic bioactivation: SULT1A1 activates pro-carcinogens such as N-hydroxyarylamines and compounds in smoked meat to highly reactive intermediates capable of forming DNA adducts 1. The enzyme's catalytic activity is modulated by functional polymorphisms (notably Arg213His) and copy number variations (CNV), with populations carrying 1-5 gene copies 3. Gene copy number differences best explain inter-individual enzyme activity variation 3. Clinically, SULT1A1 polymorphisms associate with cancer susceptibility, particularly the His/His genotype increasing breast cancer risk in Asian populations 45. Risk amplifies through gene-environment interactions: the His variant combined with high smoked meat intake synergistically increases breast cancer risk 4. SULT1A1 CNV may influence estrogen metabolism and allergic disease susceptibility 6.