EFFECTS ON RESPIRATION 



491 



during the action of the quinones. There is a fairly marked augmentation 

 of pyruvate accumulation in Fusarium by low concentrations of 1 ,4-naph- 

 thoquinone (Fig. 5-5) but these measurements were made over many days 

 and do not reflect the immediate changes, and furthermore this organism 

 has apparently an unusual pattern of metabolism (Maselli and Nord, 

 1952). Indeed, the early effect of the quinone may be a block of the EM 

 pathway, since the effect on pyruvate accumulation is delayed. The keto 

 acid level rises somewhat in yeast exposed to 0.001 raM toluquinone, but 



Fig. 5-5. Effects of 1,4-NQ on pyruvate accumulation in 

 cultures of Fusarium. (Data from Maselli and Nord, 1952.) 



as the quinone concentration is increased this effect is reversed and the 

 levels fall (Flaig and de Jong, 1960 a). It is likely that the keto acid ele- 

 vation is due not to an inhibition of utilization but to a stimulation of 

 formation from glucose. Certainly pyruvate decarboxylation in yeast is 

 not particularly sensitive to the quinones, and is not inhibited at all by 

 0.1 mM toluquinone (Hoffmann-Ostenhof and Kriz, 1949 b). Indeed, the 

 oxidation of pyruvate and the formation of C^^Og from pyruvate-3-C^^ in 

 sheep thyroid slices are stimulated by menadiol-diP at 0.09 mM (Dumont, 

 1962). 



One must constantly remember that the quinones do not compose a 

 homogeneous group with respect to their metabolic effects, and that results 

 obtained on one quinone do not necessarily apply to others. In other words, 

 one should avoid as much as possible saying that the "quinones" do this or 

 that, this implying certain common actions. Thus the interesting effects 

 of phenanthraquinone reported by Tiedemann and Risse (1960) and dis- 



