Biosynthesis of O-linked glycoproteins
This process is the step-wise addition of the sugar residues directly
onto the polypeptide chain. It occurs in the Golgi.
- At first the N-Acetylgalactosamine residue is transferred from UDP-GalNAc
to the hydroxyl group of Ser or Thr residue. It is catalyzed by N-Acetylgalactosaminyltransferase.
UDP-GalNAc is synthesized from UDP-glucose.
- Then the protein moves to the trans-Golgi vesicles where the carbohydrate
chain is elongated. The specific glycosyltransferase adds the galactose
residue to the GalNAc.
- The last steps in biosynthesis of typical O-glycans are the additions
of two N-Acetylneuramic acid (sialic acid) residues in the trans-Golgi
Biosynthesis of glycolipids also occurs in the Golgi vesicles.This
process utilize the same glycosyltransferases (for example several oligosaccharides
like ABO blood group antigens are found attached to both glycoproteins
Go to :
Biosynthesis of N-linked oligosaccharides
Biosynthesis of GPI membrane anchors