Figure 1.

Biosynthetic pathways depending on mannose-1-phosphate: N-glycosylation, GPI-anchor biosynthesis, and O-mannosylation. Mannose-1-phosphate is the product of the phosphomannomutase activity, encoded by the PMM2 gene. The steps involved in the synthesis of the lipid-linked oligosaccharides required for the N-glycosylation of proteins, and glycosylphosphatidyl inositol required for the anchor of other proteins are detailed. The genes involved in each step are indicated, and those with mutations associated with congenital disorders of glycosylation are marked in red.