. "Protein which, if defective, causes a congenital disorder of glycosylation. In the endoplasmic reticulum (ER) of eukaryotes, N-linked glycans are first assembled on the lipid carrier dolichyl pyrophosphate. The GlcNAc(2)Man(9)Glc(3) oligosaccharide is transferred to selected asparagine residues of nascent polypeptides. Defects along the biosynthetic pathway of N-glycans are associated with severe multisystemic syndromes called congenital disorders of glycosylation (CDG). The characteristic biochemical feature of CDG is defective glycosylation of glycoproteins due to mutations in genes required for the biosynthesis of N-linked oligosaccharides. Defects of the assembly of dolichyl-linked oligosaccharides or their transfer on to nascent glycoproteins form type I forms of CDG, whereas CDG type II comprises all defects of the trimming and elongation of N-linked oligosaccharides." . . "Congenital disorder of glycosylation" . .