Biomedical Engineering Reference
In-Depth Information
micofilament
KOR
Glucose
Pm
CESA
vascular
CESA
SUSY
UDPG
sucrose +UDP
Fig. 2.3
Biosynthetic model of plant cellulose [
21
]
biosynthesis in
Arabidopsis
, and SG was not the only primer of cellulose synthesis.
But, recent research showed that the mechanism of cellulose synthesis in higher
plants may belong to the second hypothesis.
Cellulose synthesis in plants is the initiation, elongation, and termination of
“
-
1,4-glycosidic chains. Under in vitro conditions, it is difficult to prove that UDP-Glu
could directly synthesize cellulose, but it is generally considered that UDP-Glu is
the substrate for it. A recent study found that SG from cotton fiber can be used as an
initial extension when cellulose synthase catalyzes glucoside chains and then forms
oligosaccharide linked with lipid, which is called SCDs. In the process of cellulose
synthesis, cellulase (KOR) cut down SG from SCD so that the
“
-1,4-glucoside chain
could extend more effectively. Further analysis showed that the catalytic subunit of
Ces
A is in one side of the cell membrane; the catalytic subunit of KOR is in the
other side. This agrees with the following mechanism:
Ces
A accepts UDP-Glu from
hyaloplasm to synthesize glucan, and then glucan crosses the plasma membrane
to be further converted under the effect of cellulose. This is another significant
discovery in understanding the molecular mechanisms of cellulose biosynthesis
[
11
].
Therefore, the current anticipated process of plant cellulose biosynthesis has
three steps: (1) Sucrose synthase associated with plasma membrane guides the
UDP-glucose to provide a substrate for the synthesis of cellulose. (2) Hexagonal
polymer is organized by the coexpressional multiple
Ces
A, and glucose monomers
are polymerized to form a glucan chain; in the meantime, the discharged UDP is
recycled to sucrose synthase. (3) KORRIGAN (KOR), a kind of cellulase relating
to the membrane, is regarded as the editor or monitor of the cellulose microfilament
and can cut defective glucan chains (Fig.
2.3
). Therefore,
Ces
A, sucrose synthase,
and the KOR protein interact with each other to coregulate the biosynthesis of
cellulose in plants [
21
].
