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Metabolic adjustment upon repetitive substrate perturbations using dynamic 13C-tracing in yeast
C A Suarez-Mendez1,2,3, C Ras4, S A Wahl5,6
1Department of Biotechnology, Delft University of Technology, Van der Maasweg, 92629 HZ, Delft, The Netherlands. casuarezmendez@unal.edu.co.
Microbial Cell Factories
|September 27, 2017
Summary
Yeast metabolism rapidly adapts to feast-famine cycles, utilizing storage carbohydrates like glycogen and trehalose to buffer fluctuations and maintain robust function. This dynamic regulation prevents substrate-accelerated death and ensures efficient energy management.
Area of Science:
- Biochemistry
- Metabolic Engineering
- Systems Biology
Background:
- Environmental conditions like substrate availability, temperature, and pH dynamically impact cellular metabolism.
- Saccharomyces cerevisiae metabolism is particularly sensitive to extracellular changes, necessitating study under dynamic conditions.
Purpose of the Study:
- To investigate the dynamic flux of central carbon metabolism and storage carbohydrate metabolism in Saccharomyces cerevisiae under feast/famine conditions.
- To understand how yeast metabolism responds to rapid, cyclic changes in nutrient availability.
Main Methods:
- Utilized dynamic feast/famine conditions with cyclic substrate perturbations.
- Employed 13C-tracer experiments to analyze metabolic flux and carbon flow.
- Monitored intracellular metabolite levels and synthesis rates, including trehalose-6-phosphate (T6P).
Main Results:
- Metabolic flux demonstrated rapid and sensitive responses to cyclic substrate availability changes.
- Cells showed immediate ATP energy charge increase upon glucose addition, avoiding ATP drop.
- Glucose uptake rate surged dramatically (170 to 4788 μmol gDW-1 h-1 in 24s), with a >100-fold increase in T6P synthesis rate.
- 13C-labeling indicated ~15% of carbon inflow was recycled via glycogen and trehalose degradation, crucial for dynamic flux regulation.
- Observed a fivefold increased flux towards the Pentose Phosphate Pathway (PPP).
Conclusions:
- Yeast metabolism employs storage carbohydrates as buffering units, akin to energy grids, to maintain robust function during dynamic feast/famine cycles.
- Approximately 15% of metabolized carbon was recycled through storage metabolism, with resource distribution differing from steady-state conditions.
- Metabolic shifts, including increased PPP flux and reversed transketolase/transaldolase activity, explain observed yield changes.
