Beta-1,3-N-Acetylglucosaminyltransferase 5 (b3GNT5)

b3GNT5 is a type II membrane protein. It exhibits strong activity to transfer GlcNAc to glycolipid substrates and is identified as the most likely candidate for lactotriaosylceramide synthase. This enzyme is essential for the expression of Lewis X epitopes on glycolipids. beta3Gn-T5 exhibited strong activity to transfer GlcNAc to glycolipid substrates, such as lactosylceramide and neolactotetraosylceramide, resulting in the synthesis of Lc(3)Cer and neolactopentaosylceramide, respectively. A marked decrease in LacCer and increase in nLc(4)Cer was detected in Namalwa cells stably expressing beta3Gn-T5. This indicated that beta3Gn-T5 exerted activity to synthesize Lc(3)Cer and decrease LacCer, followed by conversion to nLc(4)Cer via endogenous galactosylation.