91. CYTOCHROME SYSTEM 



The cytochromes are part of the terminal oxidation system <oxygen reduced by the hydrogen atoms from various 

 reduction. The energy of the various partial oxidations is used to form adenosine triphosphate (ATP) from adenosine 

 process is known as "oxidative phosphorylation." [1-3] The following schematic drawing shows some of the known 

 oxidized. 



Various 



/ substrates \ 



Various substrates _TPNH+H+^ ^ DPN+ Flavin --v. /(e.g., succinate) \ 



(e.g., glucose- \ /^ \/^ N 1 



6-phosphate) \ DehydrogenaseM Transhydrogenase^ V Dehydrogenases'*/ 



N- TPN+ -^ ^ DPNH + H+ FlavinHz Products 



/ I \ (i.e., substrates 



/ 13 In less ZH) 



Products ,, I 



/ u . . 1 lui Various ^ ' 



(substrate less 2H) ■_ . . \ 



substrates \ ^».dPNH + H+- 



■^ JT' FlavinH^ 



Products / — 

 (i.e., substrates 

 less 2H) 



I Dehydrogenases' I Dehydrogenase 

 / ^- DPN+ -^ ^ Flavin 



V 



Phosphorylating 



System I: 

 ADP+Pi — ATP 



IM^XiTae substrates are activated by DPN-specific, some by TPN-specific dehydrogenases. DPN (diphosphopyridine 

 II, respectively. /2/ Transhydrogenase catalyzes transfer of hydrogen from reduced TPN to DPN. /3/ The dotted 

 from the action of a DPN-specific dehydrogenase. /4/Succinic dehydrogenase, for example, is a typical flavoprotein 

 reduce the flavin prosthetic group of a dehydrogenase directly in the respiratory chain, or /6/ reduce the heme 

 is destroyed by BAL (British Anti- Lewisite, or 1, 2-mercaptopropanol) influences the interaction of cytochrome-b 

 A. 15] 



Contributor: Morton, R. K. 



Refe ren ces : \.\\ Chance, B., and Williams, G. R., 

 l4] Slater, E. C, Biochem. J., Lond. 45:14, 1949. 



J. Biol. Chem. 2r7:429, 1955. [2] Chance. B.. Williams 

 [5] Potter. V. R., and Reif, A. E., J. Biol. Chem. 194:287, 



126 



