Sulfotransferase that utilizes 3'-phospho-5'-adenylyl sulfate (PAPS) as sulfonate donor to catalyze the sulfate conjugation of phenolic monoamines (neurotransmitters such as dopamine, norepinephrine and serotonin) and phenolic and catechol drugs. 3'-phosphoadenylyl sulfate + a phenol = adenosine 3',5'-bisphosphate + an aryl sulfate + H(+) Homodimer. Liver, colon, kidney, lung, brain, spleen, small intestine, placenta and leukocyte. The N-terminus is blocked. Belongs to the sulfotransferase 1 family. Found in a segmental duplication on p arm of chromosome 16 giving rise to two identical copies of this gene sharing exons with SLX1A and SLX1B. The ORFs of SULT1A3 and SULT1A4 differ with only a single nucleotide change that does not alter the encoded amino acid. It is not possible to determine whether any individual polymorphism is present within SULT1A3 or SULT1A4 (PubMed:15358107).