Biology Reference
In-Depth Information
1-P to the primer is present in the reaction mixture, the successive
glycosylations occur as a propagation of polymerization to produce
the
4)-glucan chain, i.e., amylose.
Because phosphorylase has shown loose specificity for the
recognition of the structure of the glycosyl donor, the phosphorylase-
catalyzed glycosylation using different glycose 1-phosphates has been
performed to produce nonnatural oligosaccharides. For example,
the enzymatic synthesis of
α
-(1
→
-
d
-xylosylated maltooligosaccharides
by the phosphorylase-catalyzed
α
-xylosylation using Xyl-1-P was
reported (Fig. 3.10) [32]. Because the structural difference of Xyl-
1-P from Glc-1-P was only the absence of a CH
α
OH group at position
6, a high possibility for recognition of this nonnative substrate by
phosphorylase had been supposed. When the phosphorylase-
catalyzed enzymatic reaction using Xyl-1-P as a glycosyl donor
and Glc
2
as a glycosyl acceptor was carried out, xylosylated
oligosaccharides were produced, which was confirmed by the MALDI-
TOF MS and
4
1
H NMR spectra of the crude products. Furthermore,
the MALDI-TOF MS spectrum showed small peaks assignable to
the oligosaccharides consisting of two xylose units in addition to
the main peaks ascribable to the oligosaccharide having one xylose
unit. However, the aforementioned analytical data did not provide
sufficient evidence to determine the structures of the products, in
O
O
O
O
HO
HO
HO
HO
HO
OH
+
O
OH
OH
OH
OH
HO
HO
O
HO
O
P
O
O
HO
2
O
Xyl-1-P
Glc
4
phosphorylase
O
O
HO
O
HO
OH
+ inorganic phosphate
OH
OH
OH
O
HO
HO
HO
O
HO
n
α
-xylosyl-(1
�
4)-maltooligosaccharides
Figure 3.10
Phosphorylase-catalyzed
α
-xylosylation of Glc
using Xyl-1-P.
4
