Glycosyltransferase required for the biosynthesis of heparan-sulfate. The EXT1/EXT2 complex possesses substantially higher glycosyltransferase activity than EXT1 or EXT2 alone. Appears to be a tumor suppressor. Required for the exosomal release of SDCBP, CD63 and syndecan (PubMed:22660413). 3-O-{[(1->4)-beta-D-GlcA-(1->4)-alpha-D-GlcNAc](n)-(1->4)-beta-D-GlcA-(1->3)-beta-D-Gal-(1->3)-beta-D-Gal-(1->4)-beta-D-Xyl}-L-seryl-[protein] + UDP-N-acetyl-alpha-D-glucosamine = 3-O-{alpha-D-GlcNAc-[(1->4)-beta-D-GlcA-(1->4)-alpha-D-GlcNAc](n)-(1->4)-beta-D-GlcA-(1->3)-beta-D-Gal-(1->3)-beta-D-Gal-(1->4)-beta-D-Xyl}-L-seryl-[protein] + H(+) + UDP 3-O-{alpha-D-GlcNAc-[(1->4)-beta-D-GlcA-(1->4)-alpha-D-GlcNAc](n)-(1->4)-beta-D-GlcA-(1->3)-beta-D-Gal-(1->3)-beta-D-Gal-(1->4)-beta-D-Xyl}-L-seryl-[protein] + UDP-alpha-D-glucuronate = 3-O-{[(1->4)-beta-D-GlcA-(1->4)-alpha-D-GlcNAc](n+1)-(1->4)-beta-D-GlcA-(1->3)-beta-D-Gal-(1->3)-beta-D-Gal-(1->4)-beta-D-Xyl}-L-seryl-[protein] + H(+) + UDP Protein modification; protein glycosylation. Forms a homo/heterooligomeric complex with EXT1. Interacts with GALNT5. Interacts with NDST1. The EXT1/EXT2 complex is localized in the Golgi apparatus. Ubiquitous. The disease is caused by variants affecting the gene represented in this entry. The gene represented in this entry is involved in disease pathogenesis. The disease is caused by variants affecting the gene represented in this entry. Belongs to the glycosyltransferase 47 family.