Effect of aeration intensity on the biochemical composition of baker's yeast. II. Activities of the oxidative enzymes

Oura, Erkki

doi:10.1002/bit.260160906

Cited by 18 publications

(5 citation statements)

References 29 publications

(1 reference statement)

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“…However, the results indicate that no major cellular component has been left out. The values listed in are in good accordance with previously reported values for the cellular composition of S. cerevisiae (Kiienzi & Fiechter, 1972; Oura, 1972; Watson, 1976; Waldron, 1977; Furukawa et al, 1983; Verduyn et al, 1990).…”

Section: Resultssupporting

confidence: 91%

Flux Distributions in Anaerobic, Glucose-Limited Continuous Cultures of Saccharomyces Cerevisiae

et al. 1997

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A stoichiometric model describing the anaerobic metabolism of Saccharomyces cerevisiae during growth on a defined medium was derived. The model was used to calculate intracellular fluxes based on measurements of the uptake of substrates from the medium, the secretion of products from the cells, and of the rate of biomass formation. Furthermore, measurements of the biomass composition and of the activity of key enzymes were used in the calculations.The stoichiometric network consists of 37 pathway reactions involving 43 compounds of which 13 were measured (acetate, CO, , ethanol, glucose, glycerol, NH;, pyruvate, succinate, carbohydrates, DNA, lipids, proteins and RNA). The model was used to calculate the production rates of malate and fumarate and the ethanol measurement was used to validate the model. All rate measurements were performed on glucose-limited continuous cultures in a high-performance bioreactor. Carbon balances closed within 98%. The calculations comprised flux distributions at specific growth rates of 0.10 and 030 h-I. The fluxes through reactions located around important branch points of the metabolism were compared, i.e. the split between the pentose phosphate and the Embden-Meyerhoff-Parnas pathways. Also the model was used t o show the probable existence of a redox shunt across the inner mitochondrial membrane consisting of the reactions catalysed by the mitochondrial and the cytosolic alcohol dehydrogenase. Finally it was concluded that cytosolic isocitrate dehydrogenase is probably not present during growth on glucose. The importance of basing the flux analysis on accurate measurements was demonstrated through a sensitivity analysis. It was found that the accuracy of the measurements of CO, , ethanol, glucose, glycerol and protein was critical for the correct calculation of the flux distribution.

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Section: Resultssupporting

confidence: 91%

Flux Distributions in Anaerobic, Glucose-Limited Continuous Cultures of Saccharomyces Cerevisiae

et al. 1997

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“…The empirical data that are available on the biomass composition of S. cerevisiae indicated that the previously reported values for the biomass constituents varied within a 10-fold range of the values that were implemented in Yeast 7.00 model. The only exception to this is the lipids, for which even consensus molecular weights are still unavailable (Albers et al 1996 ; Bruinenberg et al 1983 ; Henry 1982 ; Oura 1972 ; Schulze 1995 ; Vaughan-Martini and Martini 1993 ). Therefore, the artificially created variations in the biomass composition, which remained within a fourfold range, still yielded results falling within the possible solution space, whose actual limits were set by the available empirical data.…”

Section: Resultsmentioning

confidence: 99%

Biomass composition: the “elephant in the room” of metabolic modelling

2015

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Genome-scale stoichiometric models, constrained to optimise biomass production are often used to predict mutant phenotypes. However, for Saccharomyces cerevisiae, the representation of biomass in its metabolic model has hardly changed in over a decade, despite major advances in analytical technologies. Here, we use the stoichiometric model of the yeast metabolic network to show that its ability to predict mutant phenotypes is particularly poor for genes encoding enzymes involved in energy generation. We then identify apparently inefficient energy-generating pathways in the model and demonstrate that the network suffers from the high energy burden associated with the generation of biomass. This is tightly connected to the availability of phosphate since this macronutrient links energy generation and structural biomass components. Variations in yeast’s biomass composition, within experimentally-determined bounds, demonstrated that flux distributions are very sensitive to such changes and to the identity of the growth-limiting nutrient. The predictive accuracy of the yeast metabolic model is, therefore, compromised by its failure to represent biomass composition in an accurate and context-dependent manner.Electronic supplementary materialThe online version of this article (doi:10.1007/s11306-015-0819-2) contains supplementary material, which is available to authorized users.

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“…pombe are similar to values reported for Sac. cerevisiae (Oura, 1972; Verduyn et al ., 1990; Pronk et al ., 1994). (a) Situation in glucose-limited chemostat cultures at D = 0.10 h −1 .…”

Section: Discussionmentioning

confidence: 99%

Metabolic fluxes in chernostat cultures of Schizosaccharomyces pombe grown on mixtures of glucose and ethanol

1996

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Simultaneous utilization of glucose and ethanol by the yeast Schizosaccharomyces pombe CBS 356 was studied in aerobic chemostat cultures. In g lucose-l im i ted cultures, respirof ermenta tive metabolism occurred at growth rates above 0.16 h-l. Although Sch. pombe lacks a functional glyoxylate cycle and therefore cannot utilize ethanol as a sole carbon source, ethanol was co-consumed by glucose-limited chemostat cultures. As a result, biomass yields increased, but not UR to the theoretical value [092 g biomass (g glucose)-l] expected if all of the acetyl-CoA produced from glucose was instead synthesized from ethanol. When ethanol accounted for more than 30% of the substrate carbon in the mixed feed, it was incompletely utilized. In mixedsubstrate cultures with a saturating ethanol fraction in the feed, the increase of the biomass yield as a result of ethanol consumption was highest at low dilution rates. This was not due to an increased specific rate of ethanol consumption at low growth rates; rather, the longer residence times at low dilution rates allowed Sch. pombe to utilize a larger fraction of the available ethanol, part of which was oxidized to acetate. Activities of gluconeogenic and glyoxylate-cycle enzymes were not detected in cell-free extracts of any of the cultures. Activities of acetaldehyde dehydrogenase and acetyl-CoA synthetase were low and of the same order of magnitude as the in vivo rates of acetate activation to acetyl-CoA. The results show that ethanol is a poor substrate for Sch. pombe, even as an auxiliary energy source.

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Effect of aeration intensity on the biochemical composition of baker's yeast. II. Activities of the oxidative enzymes

Cited by 18 publications

References 29 publications

Flux Distributions in Anaerobic, Glucose-Limited Continuous Cultures of Saccharomyces Cerevisiae

Flux Distributions in Anaerobic, Glucose-Limited Continuous Cultures of Saccharomyces Cerevisiae

Biomass composition: the “elephant in the room” of metabolic modelling

Metabolic fluxes in chernostat cultures of Schizosaccharomyces pombe grown on mixtures of glucose and ethanol

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