Identification of beta 1,3-galactosyltransferases responsible for biosynthesis of insect complex-type N-glycans containing a T-antigen unit in the honeybee

摘要

Honeybees (Apis mellifera) produce unique complex-type N-glycans bearing a Gal beta 1-3GalNAc (T-antigen) unit, and honeybee-specific N-glycans are linked to royal jelly glycoproteins. In this study, we identified two novel honeybee beta 1,3-galactosyltransferase (beta 1,3-GalT) genes responsible for biosynthesis of the T-antigen in insect N-glycans. The products of the two putative beta 1,3-GalT genes (beta 1,3-GalT1 and beta 1,3-GalT2), which were expressed in Sf21 insect cells, transferred galactose (Gal) residues to GalNAc2GlcNAc2Man3GlcNAc2-PA to form the Gal beta 1-3GalNAc unit, indicating that the identified genes were involved in biosynthesis of the beta 1-3 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.