Effects of ethanol on Saccharomyces cerevisiae as monitored by in vivo 31P and 13C nuclear magnetic resonance |
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Authors: | Maria C Loureiro-Dias Helena Santos |
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Institution: | (1) Laboratory of Microbiology, Gulbenkian Institute of Science, Ap. 14, P-2781 Oeiras Codex, Portugal;(2) Centro de Tecnologia Química e Biológica, CTQB, Apartado 127, P-2780 Oeiras, Portugal;(3) Departamento de Química, Faculdade de Ciências e Tecnologia, U.N.L., Quinta da Torre, P-2825 Monte da Caparica, Portugal |
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Abstract: | Cell suspensions of a respiratory deficient mutant of Saccharomyces cerevisiae were monitored by in vivo 31P and 13C Nuclear Magnetic Resonance in order to evaluate the effect of ethanol in intracellular pH and metabolism. In the absence of an added energy source, ethanol caused acidification of the cytoplasm, as indicated by the shift to higher field of the resonance assigned to the cytoplasmic orthophosphate. Under the experimental conditions used this acidification was not a consequence of an increase in the passive influx of H+. With cells energized with glucose, a lower value for the cytoplasmic pH was also observed, when ethanol was added. Furthermore, lower levels of phosphomonoesters were detected in the presence of ethanol, indicating that an early event in glycolysis is an important target of the ethanol action. Acetic acid was identified as responsible for the acidification of the cytoplasm, in experiments where 13C]ethanol was added and formation of labeled acetic acid was detected. The intracellular and the extracellular concentrations of acetic acid were respectively, 30 mM and 2 mM when 0.5% (120 mM) 13C]ethanol was added.Abbreviations Pi
inorganic phosphate
- Pic
inorganic phosphate in the cytoplasm
- Piv
inorganic phosphate in the vacuole
- tP
terminal phosphate in polyphosphate |
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Keywords: | Saccharomyces cerevisiae Ethanol Acetic acid Cytoplasmic pH 31P-NMR 13C-NMR |
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