Anti-STP-1 antibodies enable researchers to detect and measure the STP-1 antigen in biological samples. This target is a reported synonym of the SULT1A1 gene, which encodes sulfotransferase family 1A member 1. This protein is known to function in metabolic processes, among other biological roles. The human version of STP-1 has a canonical amino acid length of 295 residues and a protein mass of 34.2 kilodaltons, although 2 isoforms have been identified. It is reported to be localized in the cytoplasm of cells and notably expressed in the rectum, liver, duodenum, colon, and appendix. STP-1 is a member of the Sulfotransferase 1 protein family.