BIOCHEMICAL REACTIONS AND THEIR CATALYSTS 97 



but two years elapsed before the vitamin activity of nicotinamide 

 (or the corresponding acid) was established. 6 It is interesting to note 

 that, whereas in 1937 a two-year interval had separated the identification 

 of an enzyme component and its trial in the treatment of the most prev- 

 alent nutritional disease of this country, today the time that would 

 elapse between discovery of a new organic molecule essential for some 

 important enzymatic reaction and its trial in many diseases would be at 

 most a matter of weeks — an excellent illustration of the change that has 

 taken place in the last decade in the general acceptance of the enzyme- 

 vitamin relationship. 



A related concept which was early appreciated by some scientists 

 working with lower types of life, but which was long neglected by most 

 workers in the field of mammalian nutrition and physiology, was that 

 of the universal occurrence of the B vitamins and their importance to 

 all forms of life. The significance of this fact and its effect upon vitamin 

 research was pointed out in the previous section. Brilliant investigations 

 early in this century demonstrated that in their metabolism of carbo- 

 hydrates both mammalian tissues and unicellular organisms (yeast) 

 utilize almost identical series of enzymatic reactions. Had the intimate 

 relationship of nutritional factors and enzyme systems been more fully 

 appreciated, there would have been earlier recognition by all biochemists 

 of the similarity of the nutritional requirements of lower forms of life 

 and those of mammals. 



It was in the period immediately following the establishment of the 

 vitamin-enzyme relationship of riboflavin, thiamine, and nicotinic acid 

 that the complex tangle of the other B vitamins was unsnarled; the 

 biological activities of countless factors which had been reported during 

 the previous twenty years were resolved into pantothenic acid, pyridoxine, 

 biotin, p-aminobenzoic acid, inositol, and folic acid, or combinations and 

 derivatives of these substances. Since the three members of the complex 

 originally recognized were known to function as parts of enzyme systems, 

 considerable effort in a number of laboratories was directed toward 

 demonstrating that substances more recently established as B vitamins 

 were also involved in some type of enzyme reactions as yet uncharacter- 

 ized, or that these newer vitamins were present in significant amounts in 

 the purified preparations of known enzymes. Although a number of 

 suggestive leads were obtained, it was impossible as late as 1943 to 

 ascribe any definite enzymatic functions to any of these "newer" B 

 vitamins. The failure to pin these substances down to specific enzymatic 

 functions led to some speculation that it might be found that not every 

 B vitamin would exhibit its "catalytic activity" by being an integral part 



