In enzymology, a quercetin-3-sulfate 4'-sulfotransferase (EC 2.8.2.27) is an enzyme that catalyzes the chemical reaction

3'-phosphoadenylyl sulfate + quercetin 3-sulfate ${\displaystyle \rightleftharpoons }$ adenosine 3',5'-bisphosphate + quercetin 3,4'-bissulfate

Thus, the two substrates of this enzyme are 3'-phosphoadenylyl sulfate and quercetin 3-sulfate, whereas its two products are adenosine 3',5'-bisphosphate and quercetin 3,4'-bissulfate.

This enzyme belongs to the family of transferases, specifically the sulfotransferases, which transfer sulfur-containing groups. The systematic name of this enzyme class is 3'-phosphoadenylyl-sulfate:quercetin-3-sulfate 4'-sulfotransferase. Other names in common use include flavonol 4'-sulfotransferase, and PAPS:flavonol 3-sulfate 4'-sulfotransferase.

• Varin L, Ibrahim RK (July 1989). "Partial Purification and Characterization of Three Flavonol-Specific Sulfotransferases from Flaveria chloraefolia". Plant Physiology. 90 (3): 977–81. doi:10.1104/pp.90.3.977. PMC 1061831. PMID 16666908.