I'm trying to model the transport of lactate in cells (in both direction via Monocarboxylate transporters):
[Lactate]intra + [H+] <----> [Lactate]extra + [H+]
I found some data on kinetics of Lactate itself (Km and Vmax) but I don't find anything on [H+].
My initial thought was to consider [H+] as a substrate, and model the transport as a sequential ordered Bi-Bi reversible reaction (from this paper: Poole & Halestrap (1993). Transport of lactate and other monocarboxylates across mammalian plasma membranes. doi:10.1152/ajpcell.1993.264.4.c761)
But it require a lot of parameters (Ki, Km, Vmax) for each substrate involved (especially H+).
So my question is: Should I consider [H+] as a substrate or just as an external parameter that impact the direction of the flux ?
(first question on Stackexchange)