INTERMEDIARY METABOLISM AND GROWTH 



transport chain of liver mitochondria are shown in the third column of Table 3 (Chance 

 and Williams, 1956). It will be noted that although DPN^ is half oxidized and half reduced 

 when substrate and ADP are present at high concentration, cytochrome c is almost entirely 

 oxidized. Thus, as Table 3, column 4 shows, the potentials which actually obtain in the 

 mitochondria in many cases differ considerably from the standard potentials. 



The total content of DPN* and DPNHj of various tissues and tumors and the 

 ratio of oxidized to reduced DPN^ have been measured by Jedeikin and Wein- 

 house (Jedeikin and Weinhouse, 1955). Ratios of DPN^/DPNH were found to be 

 greater than i, ranging from 1.2 in rat Hver to over 20 in skeletal muscle. Tumors 

 displayed intermediate values of this ratio of 2.5 to 4.5. Likewise, the total DPN^ 

 content varied from tissue to tissue. It was high in liver, kidney, and muscle and 

 lower in spleen and brain. The DPN"^ content of a variety of transplanted tumors 

 were in the range of spleen and brain. 



HP 



2-Cytochrome oxidase -F^ 

 2- Cytochrome o-Fe 

 2-Cytochrome c- Fe 



2- Cytochrome c,- Fe 



2-Cytochrome' b-Fe*** 

 FADH 



DPN 



^02+2H+-- 



2-Cytochrome oxidase - Fe 

 2-Cytochrome o-Fe*** 

 2-Cytochrome c - Fe** 



2-Cytochrome c.-Fe*** 



2 -Cytochrome b-Fe** 

 FAD 



DRNH+H* 



+ 2H* 



Lactate Pyruvate 



Fig. 7. Electron transport chain. 



The participation of pyridine nucleotides, flavoproteins, and cytochrome pig- 

 ments in the respiratory activities of intact yeast cells and ascites tumor cells has 

 been elegantly demonstrated by Chance and collaborators (Chance, 1 953-1 954; 

 Chance and Williams, 1956). Likewise, the above mentioned components have 

 been implicated in the oxidative metabolism of liver mitochondria. Fig. 7 illustrates 

 present concepts of electron transport. 



It is cjuite probable that the electron transport system contains other components in 

 addition to the flavoproteins and cytochrome pigments. In purified preparations of rat 

 skeletal muscle, (/-a-tocopherol functions as an activator in the enzymatic reduction of 

 cytochrome c by DPNH or succinate (Nason and Lehman, 1955). Isooctane extraction 

 of the particulate enzyme fraction with the concommitant removal of only 10% of the 



