Sulfation was discovered by Baumann around 1875 when he isolated phenyl sulfate from the urine of a patient who had been treated with phenol. Although
sulfation was subsequently extensively studied in vivo, its biosynthetic mechanism remained obscure until 1956 when the structure of the co-substrate of sulfation, adenosine 3′-phosphate 5′-phosphosulfate (PAPS or ‘active sulfate’; the systematic name is 3′-phosphoadenylylsulfate) was reported by Lipmann’s group. The enzymes catalyzing the sulfation reaction, the (cytosolic) sulfotransferases, have since been purified from various sources. They are a family of separate enzymes and isoenzymes with differing but often overlapping substrate specificity.