68 A SYMPOSIUM ON RESPIRATORY ENZYMES 



the release of aerobic fermentation they found an inhibition of the 

 synthesis of higher carbohydrates from glucose. This interesting 

 observation would be still more significant if respiration were not 

 inhibited at the same time. The alternative between glucose fer- 

 mentation and synthesis to glycogen suggests that thiol compounds 

 are able to upset the normal aerobic reaction course from glucose-6- 

 phosphate over Cori-ester to glycogen, forcing the glucose mono- 

 ester into the fermentation cycle. 



With Propionibacterium pentosaceum a number of interesting 

 observations were made by Fromageot and Chaix (14). Dilute sus- 

 pensions of repeatedly washed bacteria did not ferment in the pres- 

 ence of minute amounts of oxygen. This inhibition was counteracted 

 by very small concentrations of cysteine or hydrogen sulfide. With 

 unwashed and concentrated suspensions small amounts of oxygen 

 did not affect the fermentation, but aerobically fennentation dis- 

 appeared (normal Pasteur effect, Table 4) and was released by 

 thiol compounds. They concluded that normally a substance is 

 present in bacteria which protects the fermentation system against 

 the action of small amounts of oxygen. Since with impoverished or- 

 ganisms protection can be restored with cysteine, they assumed the 

 protecting substance to be a thiol compound. With high oxygen 

 pressure the physiological concentration of the protective system is 

 not high enough to counteract the oxidative inhibition and aerobic 

 disappearance of fermentation; that is, the Pasteur effect occurs. 

 When the concentration of thiol compound is increased, the oxidative 

 inhibition is blocked again, and aerobic fermentation appears. In 

 other words, the occurrence of fermentation depends on the relative 

 concentrations of SH-compound and oxygen, respectively. 



An observation reported by Dickens (68) with pyocyanine should 

 be mentioned here. In the presence of this dye "anaerobic" glycolysis 

 of sarcoma was inhibited when measured in unpurified nitrogen 

 containing 0.3 per cent oxygen. At the same time a slight color 

 remained, indicating slight reoxidation of the dye. The color and 

 the inhibition disappeared when chromous chloride was used to ab- 

 sorb the traces of oxygen. The parallel between this phenomenon 

 and our dye-induced Pasteur effect in extracts, as well as Froma- 

 geot's effect of low oxygen pressure on propionic acid bacteria, is 

 obvious. 



Despite the complexity of dye effects on living cells (68, 69), 

 Dickens came to the conclusion that in general there is a tendency 

 for dyes with high oxidation-reduction potential to increase the 



