Pasteur effect
The Pasteur effect describes a greatly increased metabolism of D -glucose during glycolysis when oxygen is no longer available.
Background
The Pasteur effect goes back to a 1861 discovered by Louis Pasteur phenomenon. He has observed that yeasts more and faster D -glucose consumption under anaerobic conditions than under aerobic conditions. At the same time much more ethanol is produced. A similar effect can be found in higher eukaryotes. Under anaerobic conditions created in the muscle lactate, the anion of the lactic acid. Simultaneously more glucose is converted to pyruvate than in glycolysis under aerobic conditions in which the accumulation of lactate and can not be observed. The emergence of the ethanol and lactate are the consequences of alcoholic fermentation and lactic acid fermentation.
1926 Otto Warburg described this observation as " Pasteur reaction ", leading to " Pasteur effect" was later.
Importance
The activation of skeletal muscle requires energy. With an intense strain the offer is limited to oxygen, so that the energy in the form of ATP is related exclusively by glycolysis. The final reaction step, the formation of lactate to lactic acid fermentation, thereby regenerating the oxidizing agent required NAD . In the reaction of one molecule of glucose caused a total of two molecules of ATP. For an adequate supply of energy, therefore, increased amounts of glucose are metabolized.
If the cell ( again) oxygen is available, it is possible to degrade pyruvate by the citric acid cycle. In this case, due to numerous oxidation steps much NADH is produced. This and the coming of the glycolysis NADH is finally reoxidized in the respiratory chain and is further rounds in glycolysis and the citric acid cycle in again available. In this aerobic degradation about 15 times more energy is produced as the anaerobic degradation Glucoses to lactate. Consequently, the consumption is reduced to glucose, it is also not generated more lactate or ethanol.
As for the coverage of the ATP demand comparatively much less glucose must be metabolized under aerobic conditions, glycolysis is inhibited. So leads a sufficient supply of oxygen to inhibition of phosphofructokinase 1, one of the first Schrittmacherenzmye of glycolysis.
Cells, which do not have mitochondria ( red blood cells ), show no definition Pasteur effect. Tumor tissue around it by the fact that aerobic degradation pathways are disabled due to a dysregulation, which constantly lactate is produced ( Warburg effect ). This dysregulation was formed in the past approaches to a rational tumor therapy ( therapeutic hyperthermia after Manfred von Ardenne ).