• Creates LacNAc (Galβ1-4GlcNAc) the most prevelant carbohydrate epitope in mammals and also Galβ1-4Glc (lactose) in milk.
• Galβ1-4GlcNAc linkage (type 2) is widely distributed on glycolipids and glycoproteins derived from the ectoderm and mesoderm.
• B4GalT1 activity on Glc is low, but it interacts with α-lactalbumin, lowering the K_M for glucose activity by 1,000-fold. α-lactalbumin levels are high at the start and end of pregnancy.
• LacNAc structures are more prevalant in vertebrates but LacdiNAc is common in invertebrates. Additionally a single base mutation Ile/Lue to Tyr in B4GalNAc-T converts it to B4GalT1. Thus, it maybe that this enzyme evolved from an invertebrated B4GalNAcT.
• B4GalT1-deficient mice exhibit moderately decreased galactosylation and an increased expression of more branched N-glycans. The is a shift in these animals from type 2 chain (Galβ1-4GlcNAc) to type 1 chain (Galβ1-3GlcNAc) chains on the lactosamine backbone. Galactosylation of the N-glycans in the serum IgA from the B4GalT1-deficient mice was completely absent, and they spontaneously developed human immunoglobulin A nephropathy.