Voit
*et al.*, *In Silico* Biol. 5, 0010 (2004); Figure 1

Figure 1: Two linear pathways that differ in a feedback signal
with which X_{4} inhibits the production of
X_{1}. In pathway a, the production is constant
at a rate α_{1}.
With inhibition, the production becomes dependent on
X_{4}, and this dependence is quantified by the parameter
g_{14}, which is negative and has a magnitude that
directly reflects the strength of inhibition. The rate constant may also
be different, because it reflects the unit of X_{4}. If
the inhibition decreases, g_{14} approaches 0, and in the
limit, pathways a and b along with the representations
of the production of X_{1} become equivalent,
demonstrating that the S-system model for pathway a is always a
numerical special case of the model for pathway
b. |