Fig. 8. Biosynthetic pathways of protein N-glycosylation (asparagine-linked saccharides) in yeast (upper) and mammal (lower). Both organisms utilize the same starting material, i.e., Glc3Man9GlcNAc2-dolicol, but after the removal of outer Glc3M they take completely different pathways. As a result, in yeast, "high-mannose type" structures lacking galactose are constructed, whereas in mammal the common Man9GlcNAc2 precursor oligosaccharide undergoes "processing" and subsequent transfer of GlcNAc and galactose to convert the oligosaccharides into mature "complex-type" structures.