EFFECTS ON OXIDATIVE PHOSPHORYLATION 477 



competition between cytochrome c and oxygen for the hydroquinones. 

 The nature of the enzyme, the quinone used, the relative concentrations 

 of flavoenzyme, cytochrome c and quinone, and the conditions of the ex- 

 periment will determine the patterns of electron flow. The results are sum- 

 marized in Table 5-3, from which it may be observed that there may be 



Table 5-3 

 Relative Rates of REDtrcED Flavoenzyme Oxidation by Quinones" 



" All the relative rates are normalized to 100 for the maximal rate. The values for 

 Eq are as given by Mahler et al. (1955 a) and are lower than those in Table 5-1, but 

 the relative values are comparable. The enzymes used are: I = NADH:cytochrome 

 reductase, II = diaphorase. III = L-amino acid oxidase, IV = butyryl-CoA dehydro- 

 genase, V = Mo-free xanthine oxidase, and VI = xanthine oxidase with Mo added. 

 All the quinones were at 0.5 mM. 



an optimal Eq' for the acceptor, matching in some manner the flavoenzyme 

 donor, the Eq' for which varies somewhat from enzyme to enzyme. Although 

 the metal ion may not be directly involved in the quinone reaction, it 

 will also be of some importance in determining the over-all eventual elec- 

 tron flow. 



EFFECTS ON OXIDATIVE PHOSPHORYLATION 



Various quinones appear to be involved not onlj^ in electron transport 

 but in certain phosphorylations, and this provides opportunity for ex- 

 ogenous quinones to interfere with the generation of ATP directly by an 

 uncoupling action. 



Participation of Quinones in Oxidative Phosphorylation 



Mitochondria from the livers of vitamin K-deficient chicks exhibit a 

 reduced P:0 ratio (/?-hydroxybutyrate and succinate as substrates) com- 



