Pasteur effect phosphorylation

Traditionally, biologists views of cell-level responses to 02 limitation are formalized in the concept of the Pasteur effect as ATP generation by oxidative phosphorylation begins to fall off due to oxygen lack, the energetic deficit... 

Answer The addition of oxygen to an anaerobic suspension allows cells to convert from fermentation to oxidative phosphorylation as a mechanism for reoxidizing NADH and making ATP. Because ATP synthesis is much more efficient under aerobic conditions, the amount of glucose needed will decrease (the Pasteur effect). This decreased utilization of glucose in the presence of oxygen can be demonstrated in any tissue that is capable of aerobic and anaerobic glycolysis. 

This phenomenon, which is known as the Pasteur effect, has been attributed to several mechanisms (Barnett and Entian 2005). Respiration needs very high amounts of ADP inside the mitochondria as a subtract for oxidative phosphorylation. Therefore, when respiration takes place, the cytoplasm lacks ADP and inorganic phosphate (Lagunas and Gancedo 1983), which in turn decreases the sugar transport inside the cell (Lagunas et al. 1982). These mechanisms explain how aeration inhibits the alcoholic fermentation. 

The Pasteur effect includes decreased oxidative phosphorylation and an increase in anaerobic fermentation. Because fermentation produces far less ATP than oxidative phosphorylation per molecule of glucose, increased activity of the glycolytic pathway is necessary to maintain the ATP levels in the hypoxic ceUs. 

Phosphofructokinase (EC 2.7.1.30) catalyses the phosphorylation of fructose-6-phosphate to fructose-1,6-biphosphate as the key regulatory enzyme of glycolysis. Inhibition of phosphofructokinase by adenosine triphosphate and its activation by adenosine monophosphate and inorganic phosphate is held responsible for the induction of the Pasteur effect (for review see Ramaiah 1974). 

In 1941 Feodor Lynen in Munich and Marvin Johnson in Madison independently made the most significant proposal among the early attempts to account for the Pasteur effect. They proposed the theory that in aerobiosis there was a lack of phosphate because of the efficient competition of oxidative phosphorylation for the inorganic phosphate required for glycolysis. This phosphate competition hypothesis has been most vigorously championed by Racker. A related alternative possibility, competition for the nucleotide phosphate acceptor, was implicit in Johnson s paper, explicitly formulated simultaneously by Fritz Lipmann and vigorously supported by Britton Chance on the basis of the great affinity of the oxidative phosphorylation for ADP. 

Regulation of phosphofructokinase is not enough to account for the inhibition of glucose utilization in aerobiosis. An additional link was needed. And it could not be understood without the realization that there is a glucose phosphorylation pathway that involves two steps a catalysed transport and an irreversible phosphorylation. Now, control of a pathway can take place either at the level of the first step or at the first irreversible step. Of the organisms more used in studies on the Pasteur effect, in animal cells the glucose phosphorylation pathway is feedback controlled by allosteric inhibition of hexokinase by glucose- P,... 

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