BRIXTON CHANCE 



THE SEQUENCE OF RESPIRATORY ENZYMES 

 IN THE RESPIRATORY CHAIN INVOLVED 

 IN OXIDATIVE PHOSPHORYLATION 



We have recently studied the sequence of oxidation reac- 

 tions that immediately follow the rapid mixing of oxygen and 

 anaerobic mitochondria prepared from liver, and typical results 

 are illustrated by Figure 7. The top trace gives the complete 

 record from the oxidation of reduced cytochrome c (upward 

 deflection of the trace) to its reduction (downard deflection of 

 the trace) caused by the respiration of the mitochondria. The 

 speed of oxidation is measured from the magnitude of the 

 oxidation of cytochrome c and the time after mixing, as meas- 

 ured from the flow velocity trace. For the particular record 

 shown, cytochrome c is 46% oxidized at 11 millisec. after mixing 

 1 5 /xM oxygen with anaerobic mitochondria. This corresponds 

 to a pseudo first-order velocity constant of 53 sec. ~^ At pairs of 

 wavelengths appropriate to the difference spectrum of other 

 components, reaction times are measured, and velocity con- 

 stants are computed (see Table I). It is clear that the com- 

 ponents listed in this table are oxidized at speeds consistent with 



TABLE I 



Sequence of Oxidation of Reduced Enzymes in Phosphorylating and 



NONPHOSPHORYLATING PREPARATIONS. REGENERATIVE FlOW APPARATUS 



330 



