– Sulfate conjugation catalyzed by cytosolic sulfotransferase (SULT) enzymes. The SULTs are Phase II drug-metabolizing enzymes that catalyze the addition of a sulfuryl moiety to both endogenous compounds, including steroids and neurotransmitters, and certain xenobiotics, including N-hydroxy-2-acetylaminoflourine and phenolic compounds, like alpha-naphthol. SULTs may be involved in the individual genetic disposition, species differences, and organotropisms for toxicological effects of chemicals. Particularly SULT1A1 (Sulfotransferase family, cytosolic, 1A, phenol-preferring, member 1), a member of the sulfotransferase 1 subfamily, which is a major pathway for drug metabolism in humans. Humans have at least 10 functional SULT genes. There has been an explosion in information on sulfotransferase polymorphisms and their functional consequences. An Arg213His polymorphism in SULT1A1 has a strong influence on the level of enzyme protein and activity in platelets, which have been widely used for phenotyping. Statistically significant associations were observed between the SULT1A1 genotype (Arg213His) and age, obesity and certain neoplasias (mammary, pulmonary, esophageal and urothelial cancer). Furthermore, the polymorphism of the SULT1A1 may be closely associated with breast cancer.