449 



Pyrroles, Porphyrins and Related Compounds 



chrome c rather minor spectral differences were noted, 

 but there were gross differences in the amino acid com- 

 position of the protein.'"'" The prosthetic group of cyto- 

 chrome ao from Aerobacter aerogenes has been purified 

 but not crystallized/'^ Strict anaerobes such as Clostridia 

 seem to lack cytochromes, and some lactobacilli seem to 

 use flavins instead. 



Reviews of the role of cytochromes in electron transport 

 have been published. ''-• '^- '^*' °^' This process is shown in 

 outline in the accompanying diagram. 



TPN + 



TPN— DPN 



Transhy- 



drogenase 



TPNH 



DPNH. 



Succinic 



Dehydrogenase- 



FADH. 



ELECTRON TRANSPORT 



Amytal 

 Sensitive 



i 

 E-FAD 



T 



DPNH 



Dehy' 

 drogenase 



i 

 E-FADH-; 



Antimycin Cyanide 



Sensitive Pr Sensitive 



i I i 



E-2-Heme-Fe++ 2-Heme-Fe+++ E-2(Cu+)Heme 

 T \ / \/ Fe++ 



Cytochrome y Cytochrome V Cytochrome 



i 



03 

 (Oxidase) 



E-2Heme-Fe + + + 2-Heme-Fe++ E-2(Cu++)Heme- H2O 



T I T Fe+++ 



CP T Pr CP 



E-Cytochrome b 



or 

 E-Coenzyme Q 



E = Apoenzyme 

 CP = Coupled phosphory- 

 lation (ATP Synthesis) 

 Pr = Protein 



The role of Hpides and quinones in electron transport 

 has been discussed. '''' The mechanism of coupled phos- 

 phorylation is not understood in detail, but can be repre- 

 sented as follows: 



^ Martin D. Kamen and Yoshiro Takeda, Biochim. et Biophys. Acta 

 21 518 (1956). 



«i J. Barrett, Biochem. }. 64 626 (1956). 



•52 Albert L. Lehninger, The Harvey Lectures, 49 176-215 (1955); 

 idem.. Scientific American 202 102-118 (1960). 



*^^ Britton Chance and G. R. Williams, Advances in Enzymol. 17 

 65-130 (1956). 



*'^ Joseph S. Fruton and Sofia Simmons, "General Biochemistry," 

 John Wiley and Sons, New York, 1958, pp. 284-386. 



^^ David E. Green and Johan Jarnefelt, Perspectives in Biol, and 

 Med. 2 163-184 (1959). 



««D. E. Green and R. L. Lester, Federation Proc. 18 987-1000 

 (1959). 



