Chemistry Reference
In-Depth Information
belongs to the family of C-type lectins (for further information, please see Chapters
19 and 20 and also Figure 16.1h for crystal structure). The structural analysis of
an L - selectin ligand GlyCAM -1 and histochemical studies of HEVs with carbohy-
drate - specifi c antibodies suggest that the physiological L- selectin ligand requires
a 6 - sulfo sialyl - Lewis
x
( Le
x
) structure (Figure 23.2) (please see Chapter 27.4 for
selectin ligands). The key enzymes in the biosynthesis of the 6- sulfo sialyl Le
x
are
α
1,3 - fucosyltransferase ( FucT ) and GlcNAc 6 - sulfotransferase ( GlcNAc6ST ). There
are multiple isozymes of these enzymes, six
1,3 - FucTs (FucT - III - VII and IX) and
fi ve GlcNAc6STs (GlcNAc6ST- 1, HEC - GlcNAc6ST, I - GlcNAc6ST, GlcNAc6ST - 4
and C-GlcNAc6ST). The contribution of individual enzymes to the lymphocyte
homing assessed using KO mice, in which these isozymes are singly or doubly
knocked out, is summarized in Figure 23.3 [2]. This graph indicates that both
α
α
1,3 - FucTs,
FucT-VII is mainly responsible for the homing activity and FucT-IV helps to some
extent. For GlcNAc6STs, HEC- GlcNAc6ST and GlcNAc6ST - 1 contribute partially
in this order.
1,3-FucT and GlcNAc6ST are needed for lymphocyte homing. As to
α
Figure 23.2
Structure of 6 - sulfo sialyl - Le
x
determinant.
Figure 23.3
Lymphocyte homing activities to peripheral lymph nodes in
1,3 - FucT
and
α
GlcNAc6ST KO mice.
