Biology Reference
In-Depth Information
Table 2
The results of searching for all paths from eSuc to starch
with at most eleven vertices
1 SucTrans, SuSy, UGPase, NDPkin rev, StaSy(b)
2 SucTrans, SuSy, UGPase, PGM rev, StaSy(b)
3 SucTrans, SuSy, FK, Glyc(b), StaSy(b)
4 SucTrans, SuSy, FK, NDPkin rev, StaSy(b)
5 SucTrans, SuSy, FK, Adk rev, StaSy(b)
6 SucTrans, SuSy, FK, Glyc(b), StaSy(b)
7 SucTrans, SuSy, FK, PGI rev, StaSy(b)
8 SucTrans, Inv, FK, Glyc(b), StaSy(b)
9 SucTrans, Inv, FK, NDPkin rev, StaSy(b)
10 SucTrans, Inv, FK, Adk rev, StaSy(b)
11 SucTrans, Inv, FK, Glyc(b), StaSy(b)
12 SucTrans, Inv, FK, PGI rev, StaSy(b)
13 SucTrans, Inv, HK, Glyc(b), StaSy(b)
14 SucTrans, Inv, HK, NDPkin rev, StaSy(b)
15 SucTrans, Inv, HK, Adk rev, StaSy(b)
16 SucTrans, Inv, HK, StaSy(b)
In the results the transitions are given.
Considering the paths, it is conspicuous that a large number of paths go through ADP and ATP in the
same order. The ADP, which is formed by fructokinase by consuming fructose and ATP or by hexokinase
by consuming glucose and ATP, is converted again into ATP by glycolysis, NDPkin rev, and adenylate
kinase. This ATP is used for starch synthesis. Another path goes from F6P through glycolysis to starch
synthesis. But, these paths are not of interest for our question, because during the starch synthesis process
G6P is converted into starch, whereas ATP gives the necessary energy. Thus, we extend our constraints
by excluding
AT P “ e
{
SuSy
}
&no ppi & lmax
{
11
}
&e
{
AT P
}
”
or
“e
{
SuSy, ATP
}
&no ppi &
lmax
”
. ADP must not be excluded explicitly, because ADP and ATP occur together on each path.
Now, the path search yields the following two paths with a sensible biological interpretation:
1: eSuc, SucTrans, Suc, Inv, Frc, FK, F6P, PGI rev,G6P, StaSy, starch,
2: eSuc, SucTrans, Suc, Inv, Glc, HK, G6P, StaSy, starch.
These two paths are the known paths through invertase.
Sucrose-
(
re
)
-synthesis
Here, all paths to re-synthesise sucrose should be found. One search starts from UDP-glucose and the
other from glucose 6-phosphate. The search
UDPglc->Suc “e
{
11
}
{
ADP, ATP
}
&e
{
UDP, UTP
}
”
yields
the three known correct paths:
1: UGPase, PGM rev, PGI, SPS, SPP,
2: SPS, SPP,
3: SuSy rev.
The search
G6P->Suc “e
{
ADP, ATP
}
&e
{
UDP, UTP
}
”
yields the following paths:
1: PGM, UGPase rev, SPS, SPP,
2: PGM, UGPase rev, SuSy rev,
3: PGI, SPS, SPP,
There are no paths through invertase, which is correct, because the invertase driven reaction is irre-
versible.
The other paths go through PGM and PGI, which both continue through SPS and SPP, or
