BIOCHEMICAL REACTIONS AND THEIR CATALYSTS 99 



they can conveniently work with reasonable assurance that the informa- 

 tion so obtained will be of general biochemical interest and will be 

 applicable, with limitations, to other forms of life. As a matter of fact, 

 the outline of the basic reactions mentioned above was assembled from 

 information obtained from studying organisms at the extremes on the 

 scale of biological development. 



Now that it is definite that each of the B vitamins can be associated 

 with an enzymatic reaction, a pertinent question that still must be con- 

 sidered is: What clear-cut evidence is there that any of the B-vitamins 

 have fundamental roles which cannot be associated with the enzyme 

 systems in which they are known to participate? Most of the clinical 

 symptoms of deficiencies, as well as a number of miscellaneous observa- 

 tions that have been reported, have not as yet been correlated with the 

 enzymatic reactions in which the vitamins function; but there is no 

 clearly defined positive evidence that any of the typical B vitamins has 

 any indispensable roles other than those associated with the specific type 

 reactions for which it is required. In view of this it seems reasonable to 

 offer as a general hypothesis that the only function of the B vitamins 

 per se is to participate directly in certain specific enzymatic reactions. 



In addition to these basic reactions essential for every cell, there are 

 numerous "specialized" biochemical reactions which are not observed in 

 all forms of life, but which are characteristic of particular types of 

 organisms or tissues. These reactions are not necessarily needed by the 

 individual cells themselves, but they are essential if the complex organiza- 

 tion of life is to be maintained. Examples of such reactions are photo- 

 synthesis in green plants, nitrogen fixation in certain types of bacteria, 

 hormone production by glandular tissue, the reactions involved in trans- 

 mission of impulses in nerve tissue, etc. Do the B vitamins function in 

 such reactions? Information that has been obtained on this point seems 

 scant, especially when one considers the importance of many of these 

 phenomena and the amount of investigation they have received. It would 

 seem only natural that in the evolutionary development of the "special- 

 ized functions" the organism would utilize, wherever possible, the catalysts 

 already present and functioning in the basic metabolism of the cell. The 

 little information available on these functions of the vitamins is sum- 

 marized in a later chapter. 



The following sections of this chapter will be devoted to a general 

 discussion of the fundamental enzyme reactions. 



Enzymatic Reactions 



Any discussion attempting to explain in detail the mechanisms by which 

 B vitamins catalyze chemical reactions would necessarily become a 



