Involved in the biosynthesis of L2/HNK-1 carbohydrate epitope on both glycolipids and glycoproteins. 3-O-(beta-D-galactosyl-(1->3)-beta-D-galactosyl-(1->4)-beta-D-xylosyl)-L-seryl-[protein] + UDP-alpha-D-glucuronate = 3-O-(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. Homodimer. Expressed in the trachea, retina, spinal cord, hippocampus and other brain regions, and, at lower levels, in testis and ovary. Belongs to the glycosyltransferase 43 family.