The 296aa human SULTC1 protein, so named on the basis of its significant homology to a rat hepatic cytosolic sulfotranserase ST1C1, catalyzes the sulfate conjugation of many drugs, xenobiotic compounds, hormones, and neurotransmitters, and may be involved in the activation of carcinogenic hydroxylamines. This enzyme also shows activity towards p-nitrophenol and N-hydroxy-2-acetylamino-fluorene (N-OH-2AAF). SULT1C1 is expressed as a 1.4-kb mRNA in adult human stomach, kidney, and thyroid, and in fetal kidney and liver. By functional characterization of recombinant protein, it has been shown that SULT1C1 catalyzes the sulfonation of p-nitrophenol and N-hydroxy-2-acetylaminofluorene, but not dopamine, 17-beta-estradiol, or dehydroepiandrosterone.