310 A. W. FKENKEL 



least in the bacterial preparations, added vitamin K is not an essential component 

 of the photophosphorylation system; and, only when ascorbic acid is added, does 

 it become a suitable hydrogen carrier. However, reduced vitamin K itself will 

 activate the photophosphorylating system. 



Vernon : Have you determined what happens to the succinate? Does it go to 

 fumarate and stop there or is it photometabolized further? 



Frenkel: I do not know. I have been told by Mr. D. Geller that fumarate is in- 

 active in this system, and that upon addition of malonate the amount of succinate 

 required to carry out photopho.sphorylation is extremely small, malonate by itself 

 being inactive. Succinate thus appears to act in a catalj'tic manner but apparently 

 not by way of succinic dehydrogenase. 



References 



1. Vernon, L. P., and Kamen, M.D., Arch. Biochem. and Biophys., 44, 298 



(1953). 



2. Frenkel, A., /. Am. Chem. Soc, 76, 5568 (1954). 



3. Frenkel, A., /. Biol. Chem., 222, 823 (1956). 

 3b. Frenkel, A., Plant Physiol., 31, xxx (1956). 



4. Geller, D. M., and Gregory, J. D., Federation Proc, 15, 260 (1956). 



5. Rabinowitch, E., Phytosynthesis, Vol. 1, Chapter 7. Interscience, New York, 



1945. 



6. Colowick, S. P., and Kalckar, H. M., /. Biol. Chem., 148, 117 (1943). 



7. Kielley, W. W., and Kielley, R. K., /. Biol. Chem., 191, 485 (1951). 



8. Arnold, W., in Photosynthesis in Plants, J. Franck and W. E. Loomis, eds., 



Chapter 13. Iowa State College Press, Ames, Iowa. 



9. Arnon, D. I., Science, 122, 9 (1955). 



10. Smith, L., Federation Proc, 15, 357 (1956), and unpublished observations. 



