Has both beta-1,3-glucuronic acid and beta-1,4-N-acetylgalactosamine transferase activity. Transfers glucuronic acid (GlcUA) from UDP-GlcUA and N-acetylgalactosamine (GalNAc) from UDP-GalNAc to the non-reducing end of the elongating chondroitin polymer. Seems to act as a specific activating factor for CHSY1 in chondroitin polymerization. May facilitate PRKN transport into the mitochondria. In collaboration with PRKN, may enhance cell viability and protect cells from oxidative stress. 3-O-(beta-D-GlcA-(1->3)-beta-D-GalNAc-(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-galactosamine = 3-O-(beta-D-GalNAc-(1->4)-beta-D-GlcA-(1->3)-beta-D-GalNAc-(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-(beta-D-GlcA-(1->3)-[beta-D-GalNAc-(1->4)-beta-D-GlcA-(1->3)](n)-beta-D-GalNAc-(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-galactosamine = 3-O-([beta-D-GalNAc-(1->4)-beta-D-GlcA-(1->3)](n+1)-beta-D-GalNAc-(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-(beta-D-GalNAc-(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-(beta-D-GlcA-(1->3)-beta-D-GalNAc-(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-([beta-D-GalNAc-(1->4)-beta-D-GlcA-(1->3)](n)-beta-D-GalNAc-(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-(beta-D-GlcA-(1->3)-[beta-D-GalNAc-(1->4)-beta-D-GlcA-(1->3)](n)-beta-D-GalNAc-(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 Highest activities are measured with Mn(2+). Can also utilize Co(2+). Interacts with PRKN. Interacts with PRKN. Interacts with PRKN. Isoform 1, isoform 2 and isoform 3 are expressed in brain (at protein level). Belongs to the chondroitin N-acetylgalactosaminyltransferase family.