SULT1C3  Sulfotransferase 1C3, also known as ST1C3, is an enzyme that in humans is encoded by the "SULT1C3" gene. Sulfotransferase enzymes catalyze the sulfate conjugation of many hormones, neurotransmitters, drugs, and xenobiotic compounds. These cytosolic enzymes are different in their tissue distributions and substrate specificities. The gene structure (number and length of exons) is similar among family members. ST1C3 sulfates large benzylic alcohols such as 1-hydroxymethyl-pyrene to chemically reactive mutagenic sulpho conjugates.