Evidence for New beta 1-3 Galactosyltransferase Activity Involved in Biosynthesis of Unusual N-Glycan Harboring T-Antigen in Apis mellifera

In a previous study (Y. Kimura et al., Biosci. Biotechnol. Biochem., 70, 2583-2587, 2006), we found that new complex type N-glycans harboring Thomsen- Friedenreich antigen (Gal beta 1-3GalNAc) unit occur on royal jelly glycoproteins, suggesting the involvement of a new beta 1-3galactosyltransferase in the synthesis of the unusual complex type N-glycans. So far, such beta 1-3galactosyltransferase activity, which can transfer galactosyl residues with the beta 1-3 linkage to beta 1-4 GalNAc residues in N-glycan, has not been found among any eucaryotic cells. But using GalNAc sub(2)GlcNAc sub(2)Man sub(3)GlcNAc sub(2)-PA as acceptor N-glycan, we detected the beta 1-3 galactosyltransferase activity in membrane fraction prepared from honeybee cephalic portions. This result indicates that honeybee expresses a unique beta 1-3 galactosyltransferase involved in biosynthesis of the unusual N- glycan containing a tumor related antigen in the hypopharyngeal gland.