incorporating surface receptor binding into enzyme kinetics model

All - a colleague and I are modeling an extracellular enyzmatic reaction wherein some of the substrate species are in equilibrium with a group of cell surface receptors. Substrate bound to these receptors are not available for enzymatic degradation and thus at any time may be sequestered away from the modeled enzymatic pathway.

We know the equilibrium constants for these receptor-ligand interactions, but no real kinetic parameters -- all literature addresses binding in equilibrium conditions.

Does anyone have any experience including these types of behaviors in a kinetics model in simbiology?

Thanks, John

Answer 1

[Arthur Goldsipe]

When you say that the substrate is in equilibrium with the receptors, I infer that the receptor-ligand interactions are happening on a much faster time scale than the enzymatic degradation of the substrate. If that's really what you mean, then the particular rate constants for receptor-ligand interactions may be largely irrelevant, and you just need to solve the differential algebraic equations for the equilibrium constraint for receptor-ligand interaction and the dynamics of ligand degradation.

If you didn't mean to imply that there are two distinct time scales, then you'll need rate constants for receptor-ligand interactions. Fortunately, if you already have the equilibrium constant, you only need one of the rate constants, and you can calculate the other from the equilibrium constraint. If you don't yet have access to dynamic data to confirm the model, perhaps the model can guide your experimental design.