[Control of aerobic metabolism in starved yeast cells supplied with glucose and ammonia].
When glucose is added to starved yeast cells under strictly aerobic conditions ([O2]>90% air saturation) the concentrations of G-6-P, F-6-P, FDP, pyruvate, malate and α-ketoglutarate rise, whereas those of PEP and PGA fall to a low level. This indicates that PK is activated and either GAPDH or PGK becomes rate limiting. Exogenous citrate is metabolized only after feeding. The level of pyruvate, α-ketoglutarate and malate accumulated is lower if ammonia was added to the medium, which indicates the onset of amino acid synthesis. The concentrations of adenosine and uridine nucleotides are diminished if ammonia is present in addition to glucose. Actinomycin prevents the decrease in adenosine nucleotide concentrations.The accumulation of FDP and pyruvate after glucose addition is more pronounced in the presence of ammonia. This, together with changing rates of ethanol accumulation, indicates that PDC is a limiting factor during starvation and becomes activated very slowly, especially in the presence of ammonia.
Botanisches Institut der Universität, Kirschallee 1, D-5300, Bonn, Federal Republic of Germany.
S M
SM
Mizani
A
A
Betz
C
C
Eilers-König