C. A. ELVEHJEM 



dialyzability, there are no grounds for not classifying vitamins with 

 enzymes. Prior to this, Harden and Young, in 1906, emphasized the 

 importance of organic dialyzable substances in yeast fermentation and 

 called these substances coenzymes. In 1918, Meyerhof found the co- 

 enzymes of yeast to be present in a number of animal tissues; but 

 animal workers were too busy compounding rations to pay any atten- 

 tion to this finding. R. J. Williams, in 1919, concluded that the sub- 

 stance or substances which stimulate the growth of yeast are identical 

 with the substance or substances which in animal nutrition prevent 

 beriberi or polyneuritis. 



Then, in 1932, Warburg and Christian found that the so-called 

 yellow enzyme which they had shown to be active in a reconstructed 

 oxidation system contained a derivative of riboflavin, the second mem- 

 ber of the B complex, as the prosthetic group, A short time later, it 

 was found that the coenzyme used in the same system and prepared 

 from red blood cells contained nicotinic acid. In 1937, nicotinic acid 

 was shown to be the antipellagra factor and thus became identified with 

 the third member of the B complex. In 1932, Auhagen split carboxyl- 

 ase, the enzyme necessary for the metabolism of pyruvic acid, into a 

 protein component and a thermostable part called cocarboxylase. 

 Soon cocarboxylase was identified as the pyrophosphoric acid ester of 

 vitamin Bj. 



The fourth decade of the 20th century will undoubtedly be 

 recognized as the period of greatest advance in our knowledge of the 

 mechanism of action of the vitamins. We must recognize that much is 

 still unknown and that some of the most difficult problems lie ahead. 

 However, the results so far obtained have had a much broader in- 

 fluence — they have given new impetus to the study of enzyme chemis- 

 try. R. R. Williams states: "These enzyme molecules are too vast 

 and complex for the chemist to decipher completely today, but we can 

 now say that the prosthetic group or business ends of these molecules 

 are in many instances what we earlier came to call vitamins. These 

 vitamins are, therefore, the bits, the working ends, of the keys which 

 unlock stores of vital energy from glucose and other foods." The 

 enzyme approach has emphasized the close relationship of all types of 

 life. Vitamins have turned out to be growth factors and metabolic 

 regulators for plants, bacteria, protozoa and yeast, as well as for 

 animals. See W. H, Peterson, Biol. Symposia, 5, 31 (1941). 



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