Biology Reference
In-Depth Information
Chapter 4
Phosphorylase-Catalyzed Enzymatic
Polymerization
4.1
Outlines of Phosphorylase-Catalyzed
Polymerization
Amylose is expected to have uses in various industries as a
functional biomaterial. Amylose is one of the components of starch
and present with amylopectin in nature (Chapter 1). However, pure
amylose is currently not available for industrial purposes because
the separation of natural amylose from amylopectin is difficult.
Phosphorylase is the only enzyme that can produce amylose with
the desired average molecular weight (Fig. 4.1) [1]. Phosphorylases
from potato and rabbit muscle have been successfully employed in
the synthesis of amylose
[2,3]. As a glycosyl acceptor for the
initiation of the polymerization, maltooligosaccharides with DPs
higher than the smallest one, i.e., maltotetraose, which is recognized
by phosphorylase, are used. The glycosyl acceptor is often called a
“primer.” In the initiation, a glucose unit is transferred from Glc-1-P
of a monomer to a nonreducing end of the primer to form
in vitro
4)-
glycosidic linkage. Then, successive reactions in the same manner
occur as a propagation of the polymerization to produce the
α
-(1
4)-
glucan chain, i.e., amylose. Because the phosphorylase-catalyzed
polymerization proceeds analogously to a living polymerization, the
α
-(1
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