Biomedical Engineering Reference
In-Depth Information
the
-acetylated crude mixture after the treatment with GA using
HPLC. The
N
1
H NMR spectrum of the isolated material fully supported
the structure of
. In particular,
there was no signal assigned to the H-4 position of the glucose
residue at the nonreducing end of Glc
N
-acetyl-
α
-glucosaminyl-(1
→
4)-Glc
4
, whereas the signal ascribed
to the free H-4 position of GlcNAc was observed. This observation
indicated that the GlcNAc unit was positioned at the nonreducing
end bound with the
4
α
-(1
→
4)-glycosidic linkage.
using
GlcNAc-1-P as a glycosyl donor was also performed under the same
conditions as those using GlcN-1-P, the MALDL-TOF MS spectrum of
the crude products did not show peaks assignable to the molecular
masses of oligosaccharides having a GlcNAc unit. This result indicated
that the GlcNAc-1-P was not recognized by phosphorylase, probably
because the bulky acetamido group in GlcNAc-1-P blocked approach
to the active site.
However, the following study reported that 2-deoxy-2-
formamido-
Although the phosphorylase-catalyzed glycosylation of Glc
4
-glucosamine 1-phosphate (GlcNF-1-P), which had the
formamido group of a smaller substituent than an acetamido, was
recognized as a glycosyl donor by phosphorylase [41]. This allowed
the
α
N
-formyl-
α
-glucosaminylation of maltooligosaccharide to give
α
N
-glucosaminylated maltooligosaccharides (Fig. 3.15).
The MALDI-TOF MS spectrum of the crude products obtained by
the phosphorylase-catalyzed
-formyl-
α
N
-formyl-
-glucosaminylation using
GlcNF-1-P and Glc
showed only a significant peak corresponding to
the mass of a pentasaccharide containing one GlcNF unit. This data
indicated that the transfer of one GlcNF residue from GlcNF-1-P to
Glc
4
occurred. Then, the treatment of the crude products with GA
was carried out to reveal whether the GlcNF unit was positioned at
the nonreducing end. In the MALDI-TOF MS spectrum of the treated
products, the peak assigned to the molecular mass of the produced
pentasaccharide remained intact, supporting that the GlcNF unit was
positioned at the nonreducing end. Moreover, the pentasaccharide
was isolated from the crude products after the treatment with GA.
The
4
1
H NMR spectrum of the isolated material fully supported the
structure of
. The two signals
due to the formyl group were observed, which were assignable
to
N
-formyl-
α
-glucosaminyl-(1
→
4)-Glc
4
-isomers owing to hindered rotation of the formyl
C-N bond (two rotamers). For further analysis, the formation of
N
E
- and
Z
α
-formyl-
-glucosaminylated oligosaccharides vs. reaction time
