Balance of production and consumption of ATP in ammonium-starved Saccharomyces cerevisiae.
To establish a balance between the ATP produced in catabolism and the ATP consumed in net biosynthesis of cellular components the energy metabolism of Saccharomyces cerevisiae utilizing glucose in the absence of a nitrogen source (resting cells) was studied. The following results were obtained. (i) Cell number and biomass increased 2- and 2.5-fold, respectively, during the first 8 h of ammonium starvation. After this period, both values remained constant. (ii) The rate of sugar consumption and ATP production decreased with the duration of starvation to about 20% of the original in 24 h. (iii) About 60% of the sugar consumed was fermented to ethanol and about 10% assimilated as cellular material. Of the assimilated sugar, as much as 80% was accumulated as carbohydrate. (iv) Only 15% of the total ATP produced in catabolism seems to be consumed in net biosynthesis and maintenance of intracellular pH. The fate of the remaining 85% is unknown.
Lagunas
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R
Instituto de Investigaciones Biomédicas del CSIC, Facultad de Medicina de la UAM, Madrid, Spain.
Ruiz
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E
D000255:Adenosine Triphosphate / Q000096:biosynthesis / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*
D000644:Quaternary Ammonium Compounds; D000255:Adenosine Triphosphate; D005947:Glucose