Lipid-linked core precursor

Synthesis of a lipid-linked core precursor. N-Unked oligosaccharides are initially synthesized as Upid-linked precursors. The lipid component is dolichol (Dol), a long chain polyisoprenol of n = 14-24 isoprene units, which is linked to the oligosaccharide precursor via pyrophosphate bridge. 

The discovery that dolichol phosphates and pyrophosphates (diphosphates) are carriers for oligosaccharides in eukaryotic cells initiated the modem era of glycoprotein biochemistry. These lipid-linked oligosaccharides are precursors for the carbohydrate side chains of the asparagine-linked glycoproteins. Because of this common precursor, all of the side chains of these glycoproteins share the same carbohydrate core, shown within the dashed box in Figure 16-la. 

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