Protein Glycosylation: Implications for In Vivo Functions and Therapeutic Applications - Advances in Biochemical Engineering Biotechnology - page 159

Oligomannose

Complex : biantennary

Complex : triantennary
(solid lines)

Complex : tetraantennary
(solid + dotted lines)

Hybrid

Core
region

Branching
region

Terminal
region

Fig. 1. The basic forms of common N -linked glycans. The N -linked glycans posses three re-
gions of oligosaccharides - core, branching and terminal. All glycans have common core of
two N -acetylglucosamine residues and three mannose residues. N -linked glycans are primari-
ly depend on the branching pattern and the type of monosaccharides present in the branching
and terminal regions. The branches are distributed over the two terminating core mannose
residues. The complex type N -linked glycans can have two to four antennae. In complex and
hybrid type N -glycans, the antennae usually terminate in sialic acid or galactose. Sialylation
adds the greatest degree of microheterogeneity, however variable core fucosylation also adds
heterogeneity to the glycan. -GlcNAc (Gn); -Fuc; -Man; -Gal; -NueAc (SA)

3. Hybrid-type structures combine the structural features of both the high Man
and the complex-type.

2.3.1
Biosynthesis and Processing

Glycosylation begins in the rough ER and proceeds as glycoproteins migrate
through the Golgi to their final destination.Asn-glycosylation is a cotranslatio-
nal event and occurs as the polypeptide is being transferred into the ER, while