RESUMO
Honeybees (Apis mellifera) produce unique complex-type N-glycans bearing a Galß1-3GalNAc (T-antigen) unit, and honeybee-specific N-glycans are linked to royal jelly glycoproteins. In this study, we identified two novel honeybee ß1,3-galactosyltransferase (ß1,3-GalT) genes responsible for biosynthesis of the T-antigen in insect N-glycans. The products of the two putative ß1,3-GalT genes (ß1,3-GalT1 and ß1,3-GalT2), which were expressed in Sf21 insect cells, transferred galactose (Gal) residues to GalNAc2GlcNAc2Man3GlcNAc2-PA to form the Galß1-3GalNAc unit, indicating that the identified genes were involved in biosynthesis of the ß1-3 Gal-containing N-glycan. Therefore, using biochemistry and molecular biology techniques, we revealed a unique N-glycan biosynthesis mechanism in the cephalic region of honeybees, which has not previously been found in other animal or plant cells.