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The next examples of metabolic patterns are related to the regulation aspect of
reactions. The simplest form of regulation composition is shown in Fig. 3.13, which
can be seen as a regulation cascade. In the case of a regulation cascade we can speak
of a
source reaction
and of a
destination reaction
.
Fig. 3.13
A regulation chain
A regulation cascade where the source reaction coincides with the destination
reaction is a regulation cycle (see Fig. 3.14). In this case we may have a lot of pos-
sibilities in dependence of the kind of substances (reactants or products) regulating
the reactions. An important aspect of a regulator is given by its direct or inverse
character. In the first case, the flux is directly dependent on the value of the reg-
ulating substance. In the second case, it is inversely dependent on it. Two cases of
regulation cycles are represented in Fig. 3.14. Biregulation, represented in Fig. 3.15,
is another recurrent schema of regulation mechanism.
Fig. 3.14
Two regulation cycles
In the case of
antiregulation
, given in Fig. 3.16, one substance regulates the
production of another substance, which in turn, regulated the consumption of the
first one.
