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 (PubMed:12716890). 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. Ubiquitous. Highly expressed in pancreas, ovary, brain, heart, skeletal muscle, colon, kidney, liver, stomach, spleen and placenta. Expressed in brain, spleen, ovary, testis, lung and peripheral mononuclear cells. Also ubiquitous. Belongs to the chondroitin N-acetylgalactosaminyltransferase family.