LLO biosynthesis pathway in the ER lumen. Arrows mark the reactions in which dolichol-phosphate (DolP)–Man or DolP-Glc are used as substrates and where the DolP-Man–dependent transferases ALG3, ALG9, and ALG12 are involved. The complete oligosaccharide GlcNAc2Man9Glc3 is transferred from its lipid carrier to nascent polypeptides by the oligosaccharyltransferase complex (OST). Known types of CDG are marked with the respective names CDG-Ic, -Id, -Ig, and -Ih.