Enzyme speed limit
You have been flagged for exceeding the catalytic capacity of an enzyme.
Notice of excess fluxTicket EC 1.1.1.1
- Reaction
- Ethanol → acetaldehyde
- Measured flux
- v = 12.4 mmol gDW⁻¹ h⁻¹
- Speed limit
- kcat·[E] = 8.0 mmol gDW⁻¹ h⁻¹
- Excess
- 55% over the limit
- Penalty
- One additional enzyme, payable in protein
- Corrective action
- Upregulate expression, or slow down and drive responsibly
The real story. Every reaction in a cell is catalysed by an enzyme, and each enzyme molecule can only work so fast. Its turnover number, kcat, times the amount of enzyme, [E], sets an upper limit on the reaction rate: v ≤ kcat·[E]. Because the cell can only make a limited amount of protein, these limits shape how it uses its metabolism.
Our GECKO toolbox adds these enzyme constraints to genome-scale metabolic models, so predicted fluxes respect what the cell can afford (paper).