source: liacs/bpn/presentation/presentation.txt@ 22

The metabolism between sucrose and starch in the potato tuber is of great research interest. 

Even if the metabolism is one of the best studied in sink organs,
it is not yet fully understood. *WHY?*

kinetic models based on differential equations are able to simulate networks quantitatively, there are clear limitations to such models, so long as the data are incomplete. ... the detailed kinetic laws and constants are often incomplete or entirely missing.
WORKAROUND: Nearest neightboor used, estimated

 The conversion of sucrose through hexose phosphates to starch is the major  version of sucrose through hexose phosphates to starch is the major flux in potato tuber metabolism.

Phosphorylation turns many protein enzymes on and off, causing or preventing the mechanisms of diseases such as cancer and diabetes.

Hexokinases have been found in every organism checked, ranging from bacteria, yeast, and plants to humans and other vertebrates. They are categorized as actin fold proteins, sharing a common ATP binding site core surrounded by more variable sequences that determine substrate affinities and other properties. Several hexokinase isoforms or isozymes providing different functions can occur in a single species.

 In biological models, groups of certain metabolites, such as
adenylates (AMP+ADT+ATP) or uridylates (UMP+UDP+UTP) often form P-invariants.

According to the firing rule, transitions without pre-places are always enabled, so they can always fire. Thus, in the model it is assumed that sucrose is always available, and that produced starch can be consumed by or deposited in the cell.

Invariant A: UDPglc, UTP, UDP.
Invariant B: ATP, AMP, ADP. 
Invariant C: G6P, F6P, G1P, UTP, ATP(2), ADP, S6P, Pi ,PP(2). 
 Invariant C represents the set of all compounds, which provide directly or indirectly a phosphate group.

Invariants A and B comprise the metabolites containing uridine or
adenosine residues, respectively.