PASTEUR EFFECT 65 



safranine and other phenazine derivatives, Dickens (39, 48) presents 

 evidence which suggests that a flavin enzyme may participate in 

 the transmission of the aerobic inhibition. The relationship between 

 flavin and the Pasteur eflFect is indicated also by its occurrence in 

 the hemin-free Lactobacillus delbriickii (13), where flavin is the 

 only respiratory catalyst. 



The disturbance of the Pasteur effect in brain that attends a lack 

 of ionic balance represents a phenomenon of great complexity. Ash- 

 ford and Dixon (49) observed a profound metabolic change in brain 

 slices suspended in tenth molar potassium chloride. Aerobically they 

 found increased respiration and appearance of glycolysis; and 

 anaerobically, gradual and irreversible disappearance of glycolysis. 

 They correlated the metabolic changes with the well-known increase 

 in cell permeability through potassium ion (50). Dickens and 

 Greville (51) showed subsequently that the potassium effect is spe- 

 cific for brain and is not found in other tissues, and that omission 

 of calcium had a similar effect. Continuing on similar hues, Weil- 

 Malherbe (52) observed definite effects of potassium and also am- 

 monium ions at much lower concentrations than those used by 

 Ashford and Dixon. 



This effect of electrolyte on brain metabolism signifies a great 

 lability of the Pasteur mechanism. Warburg (54) has emphasized 

 that the Pasteur mechanism is universally very sensitive to un- 

 physiological surroundings. For example, in rat embryo aerobic 

 glycolysis is high in Ringer solution but low or absent in serum or 

 amniotic fluid. Effects of this type must be taken as an indication 

 that aerobic disappearance of glycolysis is the result of an easily 

 disturbed balance of reactions. 



REVERSIBLE OXIDATIVE INHIBITION OF GLYCOLYSIS IN EXTRACTS 



In order to approach experimentally the possibility that oxidative 

 inhibition might be the cause of aerobic disappearance of fermenta- 

 tion, I studied some time ago the effect of oxidizing agents on 

 glycolysis and fermentation in extracts (55, 56). It was shown that 

 the fermenting system was inactivated by small amounts of iodine 

 and quinone. By adding indophenols as oxidants inhibition in oxygen 

 was provoked, which disappeared in its absence, when the oxidizing 

 dye was reduced by constituents of the extract and through its 

 enzymatic activity. Two experiments of this type with muscle extract 

 and yeast juice, respectively, are summarized in Table 8. It appears 

 that addition of the dye reproduces a Pasteur effect, which occurs, 



