82 



J, B. CHAPPELL 



presence of io~^ m DNP only glutamate and isocitrate oxidation occur 

 at these rates; both malate (600-800 fxl. Oo/mg. N/hr.) and succinate (up 

 to 1600 ^1. Oo/mg. N/hr.) oxidation occur at considerably greater rates. 

 These results indicate that many mitochondrial oxidations are controlled 

 by the activity of the enzymes directly involved in the synthesis of ATP 

 and subsequent to the site of action of DNP. On the other hand ^-hydroxy- 

 butyrate was oxidized at only 60'^,, of the ADP-rate for other DPN 



Outside 



Inside 



/socitrate 

 dehydrogenase 



Inhibition -•- 



Fig. II. Postulated spatial relationship of some mitochondrial enz^Tnes. 



linked substrates; in this case some other factor, presumably the activity 

 of the dehydrogenase, controls the rate of oxidation. 



Acknowledgment 



I wish to thank Miss Freda Johnson for her expert technical assistance. 



References 



1. Chappell, J. B. (ig6i). To be published. 



2. Chance, B., and Williams, G. R., Advanc. Enzy7noL l.'J.i 65 (1956). 



3. Purvis, J. L., BiocJu'm. hiopliys. Acta 30, 440 (1958). 



4. Stein, A. M., Kaplan, N. O., and Ciotti, M. M.,y. biol. Chem. 234, 979 (1959). 



5. Thorne, C. J. R., personal communication (i960). 



6. Borst, P., and Slater, E. C, Biochim. hiophys. Acta 41, 170 (i960). 



7. Krebs, H. A., and Bellamy, D., Biochcm.J. 75, 523 (i960). 



8. Lardy, H. \., and Wellman, H.,7- biol. Chem. 195, 215 (1952). 



