Figure 1. Diagram of the model.

Substrate-cycle where enzymes α and β interconvert A into B (Fig. 1A), both regulated by external effectors F and T. Arrows indicate reactions, knobs indicate regulation. The kinetic parameters are: k₁ = 10⁻² s⁻¹; k_-1 = 8×10⁻³s⁻¹; k₂ = 10⁻² s⁻¹; k_-2 = 4×10⁻³ s⁻¹. For enzyme α, V_{ma x} = 1.6 mM s⁻¹, K_m = 1.5×10⁻³ mM. For enzyme β, V_max = 3.5 mM s⁻¹, K_m = 2×10⁻³ mM. Fig. 1B shows an example of a regulation scheme of the model where symbol ‘+’ indicates activation and ‘−’ inhibition. In this case is activated by F and T because R_α,F and R_α,T are greater than 1 for the set of parameters taken as an example, and β is inhibited by effector F because R_β,F is lower than 1. T has no effect on enzyme β because R_β,T is 1.