ENZYME-SUBSTRATE COMPOUNDS 



indicates that cytochrome c is above h in the respiratory chain in- 

 volved in oxidative phosphorylation. 



Slater's factor (41,63) is adequately described in non- 

 phosphorylating preparations as the component linking flavo- 

 protein to cytochrome c that is sensitive to BAL. But in phos- 

 phorylating preparations it has recently been found (7) that 

 cytochrome h links flavoprotein to cytochrome c (or c^ in both 

 the DPNH and succinate-linked systems, and (2) that the 



+ 0.02- 



490 



530 



570 

 /\ (rnp) 



Fig. 3. The spectroscopic changes in an aerobic mitochondrial suspen- 

 sion caused by addition of excess antimycin-A. 



Mitochondria were suspended in a reaction medium that contained all 

 substances necessary for oxidative phosphorylation except phosphate ac- 

 ceptor. The base line of the figure corresponds to the material before anti- 

 mycin-A treatment, the curve, just following the treatment. The peak at 

 563 m/i is caused by the reduction of cytochrome b, the trough at 550 m^, by 

 the oxidation of reduced cytochrome c (460-1-2). 



sensitive point lies between cytochrome h and the component 

 above it in the respiration chain (probably cytochrome c^. 

 Thus, in the phosphorylating system, cytochrome h fulfills the 

 requirements for Slater's factor. The minimum hypothesis 

 for an explanation of the effect of these inhibitors in the intact 

 system is that they affect the reaction 



h" + c'" > h'" + c" (9) 



321 



