Structural identifiability of models characterizing saturable binding: comparison of pseudo-steady-state and non-pseudo-steady-state model formulations.

A two-state variable model in which saturable binding takes place is studied. Two mathematical representations of the same model are considered, one a standard chemical kinetics type of polynomial system, the other a reduced model formed from the original system via a pseudo-steady-state approximation. For a particular experiment the structural identifiability of the set of unknown parameters of each model is examined using the similarity transformation approach. The analysis shows that when the pseudo-steady-state approximation is made a certain degree of structural identifiability is lost in the sense that fewer individual parameters can be uniquely identified.