Biology Reference
In-Depth Information
alternan-, reuteran-, and amylosucrases produce dextran (
α
-(1
6)-
glucan), mutan (
α
-(1
3)-glucan), alternan (
α
-(1
3)-
alt
-
α
-(1
6)-
glucan), reutinan (
α
-(1
4)-
co
-
α
-(1
6)-glucan), and amylose
(
4)-glucan), respectively (Fig. 2.6) [31]. Furthermore, the
modifications with respect to the glycosidic linkage pattern in
polysaccharide synthesis have been investigated. Amylosucrase
is the most extensively studied glucansucrase. Recombinant
amylosucrase was used to synthesize amylose from sucrose without
use of an acceptor [32]. The recombinant amylosucrase was also
used for the chain-elongation reaction in the presence of glycogen
as an acceptor [33]. The morphology and structure of the resulting
insoluble products were shown to strongly depend on the initial
sucrose/glycogen ratio.
Fructansucrases transfer the fructose units of sucrose onto
polysaccharides or appropriate acceptors with release of glucose.
Fructans, thus produced, are either levan composed of
α
-(1
β
-(2
6)-
fructan by levansucrase catalysis or inulin composed of
1)-
fructan by inulinsucrase catalysis (Fig. 2.6) [31]. Sucrose analogues,
which are nonnatural substrates with a similar glycosidic linkage
to sucrose, have been used for the synthesis of new poly- and
oligosaccharides by catalysis of sucrase-type enzymes. For this
purpose, a whole range of sucrose analogues have been prepared. A
wide range of fructansucrases recognize most of them, giving rise to
novel poly- or oligosaccharides [34,35].
β
-(2
(a)
(b)
(c)
OH
O
OH
O
O
O
HO
HO
HO
O
HO
O
OH
OH
OH
O
n
n
O
HO
HO
OH
n
(d)
(e)
O
O
HO
O
HO
HO
OH
O
HO
HO
n
n
Figure 2.6
Structures of dextran (a), mutan (b), alternan (c), levan (d),
and inulin (e).
 
Search WWH ::




Custom Search