The soluble sulfotransferases contribute to the elimination of xenobiotics, the activation of procarcinogens and the regulation of hormones by catalyzing the sulfate conjugation of these substances. Members of the three groups comprising this superfamily (namely SULT1, SULT2 and SULT3) show selectivity to certain substrate compounds. SULT1A1 (sulfotransferase family, cytosolic, 1A, phenol-preferring, member 1), also known as STP or STP1, is a 295 amino acid protein that localizes to the cytoplasm and belongs to the sulfotransferase family. Functioning as a homodimer that is expressed in brain, liver, skin and lung tissue, SULT1A1 catalyzes the sulfate conjugation of catecholamines, phenolic drugs and neurotransmitters and, via this catalytic activity, plays a role in the elimination of a variety of compounds from the body. Additionally, SULT1A1 may be involved in the activation of carcinogenic N-hydroxyarylamines, indicating a possible role in carcinogenesis.