Pasteur effect

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The Pasteur effect describes a greatly increased metabolism of D - glucose in the course of glycolysis when oxygen is no longer available.

background

The Pasteur effect goes back to a phenomenon discovered by Louis Pasteur in 1861 . He observed that yeasts consume more and faster D- glucose under anaerobic conditions than under aerobic conditions. At the same time, a lot more ethanol is also produced. An analogous effect can be found in higher eukaryotes . Under anaerobic conditions, the muscles produce lactate , the anion of lactic acid . At the same time, more glucose is converted into pyruvate in glycolysis than under aerobic conditions, in which an accumulation of lactate can no longer be observed. The formation of ethanol or lactate is the result of alcoholic fermentation or lactic acid fermentation (see also: Fermentation ).

In 1926 Otto Warburg referred to this observation as the “Pasteur reaction”, which later became the “Pasteur effect”.

meaning

Operating the skeletal muscle requires energy. In the case of intensive use, the supply of oxygen is limited, so that the energy in the form of ATP is obtained exclusively through glycolysis. The last reaction step, the formation of lactate in the lactic acid fermentation, regenerates the required oxidizing agent NAD + . When one molecule of glucose is converted, a total of two molecules of ATP are created. For a sufficient supply of energy, increased amounts of glucose are metabolized.

If the cell has (again) oxygen available, it is possible to break down pyruvate through the citric acid cycle. A lot of NADH is generated due to numerous oxidation steps . This and the NADH from glycolysis are finally reoxidized in the respiratory chain and are available for further rounds of glycolysis and the citric acid cycle. This aerobic breakdown generates approx. 15 times more energy than the anaerobic breakdown of glucose to lactate. As a result, the consumption of glucose decreases, and lactate or ethanol is no longer generated.

Since comparatively less glucose has to be metabolized to meet the ATP requirement under aerobic conditions, glycolysis is inhibited. A sufficient supply of oxygen leads to an inhibition of phosphofructokinase 1 , the pacemaker enzyme of glycolysis.

Cells that do not have mitochondria ( erythrocytes ), by definition, show no Pasteur effect. Tumor tissue circumvent it by switching off aerobic degradation pathways due to a dysregulation, which means that lactate is constantly produced ( Warburg effect ). In the past, this dysregulation formed approaches for a rational tumor therapy ( therapeutic hyperthermia according to Manfred von Ardenne ).

literature

Individual evidence

  1. ^ H. Robert Horton, Laurence A. Moran, K. Gray Scrimgeour, Marc D. Perry, J. David Rawn, Carsten Biele (translator): Biochemie. 4th updated edition. Pearson Studium, 2008, ISBN 978-3-8273-7312-0 , pp. 470f.
  2. ^ A b E. Racker: History of the Pasteur effect and its pathobiology. In: Mol Cell Biochem. 5 (1-2), 1974, pp. 17-23. PMID 4279327 . doi: 10.1007 / BF01874168
  3. ^ David Nelson, Michael Cox: Lehninger Biochemie. 4th, completely revised and exp. Edition. Springer, Berlin 2009, ISBN 978-3-540-68637-8 , pp. 714f.
  4. ^ O. Warburg in: Biochem. Z. 172, 1926, pp. 432-441.

See also