Beta-1,3-N-acetylglucosaminyltransferase involved in the synthesis of poly-N-acetyllactosamine. Catalyzes the initiation and elongation of poly-N-acetyllactosamine chains (PubMed:9892646). Probably constitutes the main polylactosamine synthase (PubMed:17890318). a beta-D-galactosyl-(1->4)-N-acetyl-beta-D-glucosaminyl derivative + UDP-N-acetyl-alpha-D-glucosamine = an N-acetyl-beta-D-glucosaminyl-(1->3)-beta-D-galactosyl-(1->4)-N-acetyl-beta-D-glucosaminyl derivative + H(+) + UDP Protein modification; protein glycosylation. Interacts with B3GNT8; this interaction greatly increases B3GNT2 catalytic activity, independently of B3GNT8 enzymatic activity. Expressed in heart, brain, lung, kidney and testis and, to a lesser extent, in liver and skeletal muscle. No expression in spleen. Strongly reduced number polylactosamine structures on N-glycans in immunological tissues. B-cells and T-cells proliferate show hyperproliferation (PubMed:17890318). Mice also display defective accessory olfactory bulb innervation (PubMed:23006775). Impaired sexual behaviour. While female mice are fertile, males show a reduced rate of reproduction. Defects cannot be attributed to any physical defect in their reproductive organs, suggesting that the phenotype observed may result from an impaired sexual response to female mating partners. Belongs to the glycosyltransferase 31 family. There is some conflicting nomenclature, as some groups still name this protein B3gnt1 (PubMed:18008318). The correct and official nomenclature is however B3gnt2. MGC32391: hypothetical protein MGC32391/hypothetical protein MGC32391 beta 3 GlcNAc-T I