Biology Reference
In-Depth Information
were higher than those from Glc-1-P. The molecular weight of
amylose was strictly controlled by the sucrose/primer molar ratio.
Furthermore, the
of the amylose of all sizes was close to 1,
indicating that all the synthesized amylose had a narrow molecular
weight distribution, which is same as that of amylose produced using
Glc-1-P. The amyloses with molecular weights less than 71
M
/
M
w
n
3
×
10
were produced as insoluble particles, while those with molecular
weights more than 305
were produced in the solution. These
results suggested that the properties of amylose differ according to
the molecular weights.
For the purpose of providing Glc-1-P, use of cellobiose
phosphorylase combined with phosphorylase was also examined
(Fig. 9.1). Cellobiose phosphorylase catalyzes a phosphorolytic
reaction of cellobiose in the presence of Pi to produce Glc-1-P
and glucose [8]. When partially purified cellobiose phosphorylase
was incubated with cellobiose and phosphorylase in the presence
of Pi, various sizes of amylose (from 4.2
×
10
3
×
4
×
5
) were
produced [6,7]. However, the yield (38.6%) was not as high as that in
the aforementioned method using sucrose phosphorylase. In order
to improve the yield of amylose, mutarotase and glucose oxidase
were added to the initial reaction mixture [9]. These enzymes were
expected to remove the glucose derived by the cellobiose-catalyzed
reaction, and thus, shift the equilibrium state to phosphorolysis. The
yield of amylose increased to 64.8% by the action of these enzymes.
Cellulose is the most abundant biomass resource on the earth, and
its effective use is an important research project, leading to the
sustainable society in the future. On the basis of this viewpoint, the
conversion of cellobiose into amylose is of great interest.
10
to 7.3
10
9.3
Synthesis of Branched Glucan by Combined
Use of Phosphorylase with Branching
Enzyme
Branching enzyme (BE, EC 2.4.1.18) catalyzes transfer of the glucan
chain from one
α
-(1
4)-glucan molecule to a glucan acceptor to form
6)-linkage. The enzyme activity is widely distributed
in bacteria, yeasts, plants, and animals, which is responsible for
the formation of branching structure in amylopectin and glycogen.
The BE genes from several thermophilic microorganisms, such
a new
α
-(1
