FIG. 3.
Comparison of the sensitivities to product concentration between an enzyme exhibiting reversible Michaelis-Menten kinetics and a symmetrical facilitated diffusion carrier. P is the product concentration, which is normalized to its affinity constant for the protein, Kp. The rates of the enzymes are normalized to the forward Vmax. The equilibrium constant is set to 1 for both enzymes. For the transporter, Ki was set to 0.91 (see Appendix). Solid lines indicate the Michaelis Menten enzyme; dotted lines indicate the transporter. The substrate concentration S was either set at the affinity constant Ks, for the enzyme towards the substrate (A and B) or at 100 times the affinity constant (C and D), i.e., S/Ks = 1 or 100, respectively.