Ammonia assimilation in S. cerevisiae under chemostatic growth.

Glutamate, glutamine, and ammonia pool size have been determined in two S. cerevisiae strains (GOGAT+ and GOGAT-) growing under ammonia excess and limitation at a dilution rate of 0.10/h. The biomass levels and glutamate dehydrogenase NADPH-dependent (NADPH-GDH) activities were also measured for both strains. The strain that lacks GOGAT activity showed lower levels of metabolites under both media and lower levels of biomass under carbon limitation (ammonia excess) compared to the GOGAT+ strain. Under nitrogen limitation, the biomass level was the same for both strains, but GOGAT- changed from rounded to ellipsoidal cells.