PASTEUR EFFECT 59 



After adaptation to the new environment the lactate level of the 

 blood becomes normal. Even with exhausting work the lactic acid 

 concentration remains very low, 2 to 3 millimolar, as compared with 

 a blood level of 13 millimolar reached with exhausting work at sea 

 level (Figure 2). Apparently a special mechanism prevents the 

 muscle from utilizing too much of the anaerobic energy supply even 

 at low oxygen pressure. Dill in his book on life at high altitudes (26) 

 makes interesting comments on this phenomenon: "It is as though 

 the body, realizing the delicacy of its situation with regard to oxygen 

 supply, sets up an automatic control over anaerobic work which 

 renders impossible the severe acid-base disturbances which can be 

 voluntarily induced at sea level." 



Interpretation of the Pasteur Effect 



During recent years discussion has centered more or less around 

 the question whether the effect depends upon respiratory activity 

 as such, or upon an inhibition produced by the action of oxygen. 

 In the first case the rate of respiration with its output of energy 

 would be a determining factor and a state of dynamic equilibrium 

 would result; part or even all of the respiration energy would be 

 spent or fixed to revert or repress glycolytic breakdown. If, however, 

 the effect is brought about through oxygen, or more specifically by 

 oxidative inhibition of an essential part of the glycolytic enzyme 

 system, then the reaction may be independent of the rate of respira- 

 tion and involve no transfer of energy. 



equilibrium schemes 



A fuller understanding of the partial reactions involved in fer- 

 mentation and respiration has given new impulse to the discussion 

 of their interrelationship as manifested in the Pasteur effect. The 

 fact that cozymase and adenylic acid, the two transmitter substances 

 in fermentation, are likewise participants in respiration has given 

 rise to some interesting suggestions. 



Ball (27) has pointed out that, aerobically, respiratory oxidants 

 such as flavin may compete with pyruvic acid for the reduced 

 cozymase. Pyruvic acid would disappear largely through oxidation 

 rather than through fermentative reduction. Adler and Calvet (28), 

 however, comparing the ratio of oxidized to reduced cozymase in 

 aerobic and in anaerobic baker's yeast found no significant differ- 

 ence, but a ratio of nearly one to one in both cases. 



Adenylic acid, the other common transfer system, was first linked 



