238 THE BIOCHEMISTRY OF B VITAMINS 



relation of the chemistry of the photosynthetic process with that of 

 certain chemosynthetic mechanisms which have been well established. 56 

 Chemosynthesis, the assimilation of carbon dioxide by reactions which 

 utilize energy derived from other metabolic reactions rather than radiant 

 energy, is the result of the reversal of the processes in which there are 

 decarboxylation reactions; hence the accomplishment of carbon dioxide 

 fixation by chemosynthetic means is dependent upon exactly the same 

 vitamins and enzymes that carry out these carboxylation reactions. It 

 seems reasonable to expect that many, if not most, of the photosynthetic 

 "dark reactions" which take place after the initial "light reaction" and 

 lead to the ultimate formation of carbohydrates will be reactions that are 

 the reverse of those used for carbohydrate catabolism, and hence will be 

 catalyzed by the same enzymes and cofactors. When the mechanisms 

 which the photosynthetic and chemosynthetic processes have in common 

 are eventually established, then at least some of the functions of the B 

 vitamins in photosynthesis will have been determined. 



Bioluminescence is the result of the action of an enzyme (luciferase) 

 upon a reduced substrate, dihydroluciferin, in the presence of oxygen. 57 



luciferase 



luciferin-2H+0 2 > Iuciferin+H 2 2 



The release of energy in the form of light is a specific characteristic of 

 the enzyme, since the oxidation of dihydroluciferin by other agents is not 

 accompanied by the emission of light. The reduced coenzymes of nicotinic 

 acid and riboflavin as well as sodium dithionite and hydrogen (Pt cata- 

 lyst) can be used in place of dihydroluciferin as hydrogen donors for the 

 luminescent reaction. Luciferin, though once postulated to be a flavin-like 

 compound, is now known to be chemically related to vitamin K. 58 



Bibliography 



1. Meyerhof, 0., Biol. Symposia, 5, 141 (1941). 



2. Evans, E. A., Jr., Biol. Symposia, 5, 157 (1941). 



3. Barron, E. S. G., Advances in Enzymol, 3, 149 (1943). 



4. Krebs, H. A., ibid., 3, 247 (1943). 



5. Stotz, E., ibid., 5, 129 (1945). 



6. Sumner, J. B., and Somers, E. F., "Chemistry and Methods of Enzymes," 



Academic Press, Inc. (New York), 1943, pp. 302-331. 



7. Baldwin, E., "Dynamic Aspects of Biochemistry," Macmillan Company (New 



York), 1947, pp. 305-383. 



8. Cori, C. F., Biol. Symposia, 5, 131 (1941). 



9. Woods, H. G., and Werkman, C. H., Biochem. J., 32, 1262 (1938). 



10. Lipmann, F., Cold Spring Harbor Symposia Quant. Biol., 7, 248 (1939). 



11. Lipmann, F., Advances in Enzymol., 6, 231, (1946). 



12. Lardy, H. A., and Elvehjem, C. A., Ann. Rev. Biochem., 14, 1 (1945). 



13. Lynen, F., and Franke, W., Z. physiol. Chem., 270, 271 (1941). 



14. Negelein, E., and Gerischer, W., Biochem. Z., 284, 289 (1936). 



