Additive and dominance gene effects described by a logistic function in concentration-limited metabolic pathways at steady state out of equilibrium

Stationary-state metabolite concentration in an n-step linear metabolic pathway is a logistic function of internal enzyme concentrations, with a dominance regime shift driven by Ee saturation.

• Why it matters: Additive and dominance gene effects are central to phenotype, but their mechanistic link to enzyme kinetics under mass limitation and out-of-equilibrium steady state is unclear.
• What they did: The authors modeled stationary-state flux using coupled reversible Michaelis-Menten for internal enzymes (Ei) and irreversible Michaelis-Menten for external enzymes/transporters (Ee), fitting logistic (plus Gaussian) forms to simulated and amylose data.
• The result: The logistic inflection point depends on total system mass and Ee saturation, explaining negative, partial, and complete dominance; instability occurs as Ee→0, and Gaussian peaks support overdominance and dominance reversals.