Biology Reference
In-Depth Information
OH
O
HO
HO
OH
OH
O
+
inorganic phosphate
OH
O
HO
O
OH
O
HO
OH
n
+1
OH
α
-(1
�
4)-glucan (DP = n + 3)
(α
-glucan) phosphorylase
OH
OH
O
O
HO
HO
OH
HO
HO
+
O
OH
O
OH
OH
O
P O
O
O
HO
O
OH
O
HO
Glc-1-P
OH
n
OH
α
-(1
�
4)-glucan (DP = n + 2)
Figure 3.2
Catalysis of phosphorylase.
The second well-studied phosphorylase-type enzyme is sucrose
phosphorylase, which catalyzes the reversible phosphorolysis
of sucrose into Glc-1-P and fructose in the presence of inorganic
phosphate (Fig. 3.3) [7,8]. Therefore, this enzyme has been used
with Glc-1-P and fructose for the synthesis of sucrose. Sucrose
phosphorylase is found in bacterial cells and is considered to
be involved in the metabolism of extracellular sucrose. The
phosphorolysis reaction proceeds via a ping-pong bi-bi mechanism
and the enzyme transfers
α
-glucosides even in the absence of
inorganic phosphate [9]. Taking into consideration the reaction
mechanism, sucrose phosphorylase is an
α
-glucosyl transferase
that also transfers glucose to phosphate [10-12]. This enzyme
shows strict substrate specificity with only sucrose, Glc-1-P, and
α
-
d
-glucosyl fluoride as a glycosyl donor. However, broad acceptor
specificity was found in different studies. Using this enzyme in a
transglucosyl manner, several
α
-glucosides have been synthesized
in one step from sucrose and various glycosyl acceptors.
