A catalytically inactive β1,4-N -acetylglucosaminyltransferase III (GnT-III) behaves as a dominant negative GnT-III inhibitor

摘要: β1,4-N-Acetylglucosaminyltransferase III (GnT-III) plays a regulatory role in the biosynthesis of N-glycans, and it has been suggested that its product, bisecting GlcNAc, is involved variety biological events as well regulating oligosaccharides. In this study, was found, on basis sequence homology, GnT-III contains small region significantly homologous to both snail β1,4GlcNAc transferase β1,4Gal transferase-1. Subsequent mutational analysis demonstrated an absolute requirement for two conserved Asp residues (Asp321 Asp323), which are located most rat GnT-III, enzymatic activity. The overexpression Asp323-substituted, catalytically inactive Huh6 cells led suppression activity of␣endogenous but no significant decrease expression, specific inhibition formation bisected sugar chains, shown by structural total N-glycans from cells. These findings indicate mutant serves dominant negative effect step N-glycan biosynthesis. This type ‘dominant glycosyltransferase’, identified potential value powerful tool defining precise roles GlcNAc structure.