Overflow metabolism originates from growth optimization and cell heterogeneity

Area of Science:

• Metabolic Engineering
• Systems Biology
• Biochemistry

Background:

• Fast-proliferating cells exhibit overflow metabolism (Warburg effect), using fermentation despite oxygen availability, a phenomenon lacking clear explanation.
• This metabolic strategy is observed across diverse organisms, posing a classic problem in understanding cellular energy biogenesis.

Purpose of the Study:

• To provide a quantitative explanation for overflow metabolism by integrating growth optimization and cellular heterogeneity.
• To elucidate the underlying mechanisms driving the choice between respiration and fermentation under varying nutrient conditions.

Main Methods:

• Development of a mathematical model for optimal protein allocation.
• Incorporation of heterogeneity in enzyme catalytic rates among cells within the model.
• Quantitative validation of model predictions using experimental data from *Escherichia coli*.

Main Results:

• The model quantitatively explains the growth rate dependence of fermentation flux and enzyme allocation.
• Cellular heterogeneity in enzyme kinetics is shown to be a key factor in overflow metabolism.
• The model successfully explains the Crabtree effect in yeast and the Warburg effect in cancer cells.

Conclusions:

• Overflow metabolism can be understood as a strategy for optimizing cellular growth under specific conditions, influenced by cell heterogeneity.
• The developed model offers a unified framework for understanding metabolic strategies across different organisms and conditions.
• This research provides a foundation for addressing challenges related to metabolic heterogeneity in various biological systems.