The tyrosylprotein sulfotransferases TPST-1 and TPST-2 catalyze the sulfation of tyrosine residues within secreted and membrane-bound proteins, such as cell adhesion molecules, G-protein-coupled receptors, coagulation factors, serpins, extracellular matrix proteins, and hormones. Although both TPST-1 and TPST-2 utilize 3’-phosphoadenosine 5’-phosphosulfate as their sulfate donor, they differ in their substrate specificity.