Chemistry Reference
In-Depth Information
Table 7.3
O
-Glycan chain extension as backbone structures.
Type
Structure
Name
Type 1
Gal
β
1,3GlcNAc
Type 2
N
- acetyllactosamine
Gal
β
1,4GlcNAc
i
-
antigen
Poly
N
- acetyllactosamine type 2
(Gal
β
1,4GlcNAc
β
1,3 - )
n
Branched
N
- acetyllactosamine type 2
I - antigen
Galβ1,4GlcNAcβ1,6
Galβ1
Gal
β
1,4GlcNAc
β
1,3
terminal, branch-end domain (Table 7.4 ). Tables 7.2 - 7.4 show the sequence struc-
ture of these domains and a selection from the many branch-end motifs is col-
lected in Table 7.4 .
Eight core structures have been identifi ed and are shown in Table 7.2. Core 1
and core 2 are the most common, with lower occurrence of cores 3 and 4, while
the remaining structures are relatively rare. The different cores show a cell- and
tissue - specifi c pattern which relates to their biological function [1-3]. Each core
determines the fi nal structure of the extended and completed glycans formed
through the common biosynthetic pathways outlined in Figure 7.1. Branched
chains are derived from core 2 and core 4, and are extended through the biosyn-
thetic pathways. Larger glycans are extended by Gal
1,3/4GlcNAc repeat units and
are shown in Table 7.3. The enormous variety of
O
- glycan oligosaccharide struc-
tures derives from the decoration of the core and backbone units. These modifi ca-
tions include fucosylation, sialylation, sulfation, acetylation and methylation. The
structures of a selected number of branch-end motifs are given in Table 7.4. In
addition to the sequence structural variation, the sialic acids exist as a family of
β
