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). ; [Isoform 2]: May facilitate PRKN transport into the mitochondria. In collaboration with PRKN, may enhance cell viability and protect cells from oxidative stress.