Ricerc@Sapienza

We show some recent results related to the application of singular perturbation techniques in the framework
of the so-called total quasi-steady-state approximation (tQSSA) for the approximation of some important enzyme reactions:
the fully competitive inhibition, the Goldbeter-Koshland cycle, the double phosphorylation mechanism. We determine the
uniform expansions up to the first order in terms of appropriate perturbation parameters, related to the initial conditions and
to the kinetic parameters characterizing the reactions.

The complex intracellular signal transduction networks can be decomposed into simpler moduli, where fundamental reactions, like the Goldbeter-Koshland
switch (which models, for example, the phosphorylation-dephosphorylation cycle) (1; 2), the competitive inhibition (3) and the double phosphorylation mechanism