Chemistry Reference
In-Depth Information
Figure 5.2
The
N
- glycosidase reaction mecha-
nism.
N
-Glycosidase cleaves the bond between
the N and C of the Asn to which the
N
- glycan
is bound. Thus, the released
N
- glycan has an
NH
2
at the reducing end and the Asn changes
to Asp. The NH
2
can then be non-enzymatically
removed as ammonia.
Figure 5.3
Modifi cation of the reducing end of
glycans. (a) and (b) The reducing end of an
N
-glycan, which is the binding site for proteins,
has a sugar residue that is always
N
- GlcNAc,
and this is changed to aldehyde. Few aldehyde
structures exist in biomaterials that do not
include a saccharide group, and this saccharide
at the reducing end provides a good target for
labeling and, in particular, for purifi cation. (c)
Oxime or hydrazide structures react with alde-
hyde. Materials possessing an oxime or hydra-
zide functional group can be used to capture
saccharides. (d) The aldehyde also reacts with
amine reagents (for example, 2-aminopyridine)
and the structure is then protected by reducing
agents.
