Non-Classical (Bio)Chemical Kinetics not Requiring Multitude of Structural Ligand-Binding Sites

Only the models with multiple ligand-binding sites (if the concentration of the enzyme or receptor is assumed to be low) are known to yield non-classical kinetics. A qualitative non-classic model of Rabin (1967) in which four conformational (non-structural) states are considered has been presented in a quantitative form. The model contains three extra (compared to the classical one) parameters. It can be reduced to the classical one by changing the parameters. Khl’s Recovery Model (1994) has been simplified, assuming the duration of the (obligatory) recovery phase of the receptor or enzyme (macro)molecule to be a random value distributed exponentially like the other model parameters; the model contains two extra parameters; it can be reduced to the classical one. The modified Khl’s model has been shown to retain all the essential properties of the original one, except for the ability to yield asymmetric doseresponse curves (if plotted in semi-logarithmic scale). Both models yield a diversity of non-classical dose response curves both with a higher and lower steepness. The bi-state model in which the protein concentration is assumed to be high, yields non-hyperbolic kinetics as well; the model is reduced to hyperbolic one if the protein concentration is assumed to be low.