The function of B3GNT8 (UDP-GlcNAc:betaGal beta-1,3-N-acetylglucosaminyltransferase 8, ENSG00000177191) is as follows. Beta-1,3-N-acetylglucosaminyltransferase that functions in the elongation of specific branch structures of multiantennary N- glycans. Has strong activity towards tetraantennary N-glycans and 2,6 triantennary glycans. {ECO:0000269|PubMed:15620693, ECO:0000269|PubMed:15917431, ECO:0000269|PubMed:18826941}.