Chapter IB 



BIOCHEMICAL REACTIONS AND THEIR CATALYSTS 



When a mammal or some lower form of life is deprived of an adequate 

 amount of one of the B vitamins it requires, serious changes in the 

 metabolism of the organism occur.* The deviations from the normal 

 processes induced by the deficiency are reflected in a variety of physio- 

 logical effects, many of which can be readily detected. In general, how- 

 ever, the different changes which are observed in even a simple deficiency 

 of a single vitamin are so diverse in character that it is impossible to 

 relate the symptoms physiologically or to establish any connection be- 

 tween the chemical structure of the vitamin and its physiological effects. 

 An excellent illustration of the complex nature of vitamin function is the 

 variation in the ways by which a deficiency manifests itself, not only in 

 different types of life but even among members of the same species (see 

 Chapter VI C) . Before any plausible explanations for these diverse physi- 

 ological and clinical effects of the vitamins can be deduced, it is necessary 

 to explore much deeper and uncover the specific chemical or physical 

 reactions in which they are participating. 



The elucidation of the specific manner in which a vitamin performs its 

 duties in a biological system usually does not arouse the popular interest 

 that attends the discovery of a vitamin or the accomplishment of its 

 synthesis. Nevertheless, for the medical sciences, understanding exactly 

 how these compounds work, and why, is just as important as knowing 

 what they are. Until the specific chemical functions of a vitamin are 

 determined, knowledge about the vitamin is indeed incomplete. 



The purpose of this section, then, will be to review those investigations 

 which have been reported which we feel to be most pertinent in answering 

 the question, "Into what specific reactions does each B vitamin enter?" 

 and to correlate these chemical reactions with the observed effects of the 

 vitamins upon the metabolism of cells and tissues. 



During the early investigations on essential dietary factors, it was only 

 natural that relatively little experimental work was done on the bio- 



* A number of topics which will be referred to from a general viewpoint in this 

 chapter are discussed in more detail in other parts of the book where they are 

 documented with references to the original publications. The citation of references 

 in this chapter will be limited for the most part to material not elaborated upon 

 more thoroughly elsewhere. 



95 



