Fig. 3.

Tyrosine sulfation by tyrosylprotein sulfotransferase (TPST). TPST catalyzes the transfer of sulfate from the sulfate donor 3′-phosphoadenosine-5′-phosphosulfate (PAPS) to the hydroxyl group of a tyrosine residue to form a tyrosine sulfate ester and adenosine 3′, 5′-diphosphate (PAP). R₁ and R₂ represent peptide chains.