Heparan sulfate glucosamine 3-O-sulfotransferase 5 (HS3ST5)

Sulfotransferase that uses 3'-phospho-5'-adenylyl sulfate (PAPS) to catalyze the transfer of a sulfo group to place 3 of glucosamine residues in heparan. Catalyzes the rate limiting step in the biosynthesis of heparan sulfate (HSact).

This modification is a crucial step in the biosynthesis of anticoagulant heparan sulfate as it completes the structure of the antithrombin pentasaccharide binding site. Also generates GlcUA- GlcNS or IdoUA-GlcNS and IdoUA2S-GlcNH2.