f 



THE IMPORTANCE OF "IMPURITIES" AND TRACE SUBSTANCES 71 



this chapter give the various vitamins and hormones at present 

 known, with some information as to their nature and action, but 

 with no suggestion of finality in this continually advancing field. 

 Professor David E. Green of Columbia University, in a recent ad- 

 dress 13 on physiological function from the standpoint of enzyme 

 chemistry, stated: 



"Vitamins B^ B 2 , B , and the P-P [pellagra-preventive] factor, have 

 all been shown to be the prosthetic groups of certain enzyme systems. 

 When these vitamins are not available in the diet, the active enzymes 

 cannot be formed in the cell. In consequence of the failure of these 

 enzyme systems to function properly, an abnormal physiological situ- 

 ation develops, which, if uncorrected, will lead to death. Which 

 organ first registers the effect of a particular deficiency is determined 

 by the amount of the reserves of enzymes containing the vitamin and 

 by the relative importance of this set of enzymes in the economy of the 

 organ. Thus, in B x deficiency in the pigeon, the brain is the first 

 organ to register disturbed function, presumably because there are no 

 reserves of this vitamin in the brain and because the enzyme formed 

 by the vitamin plays a key role in the metabolism of the brain. One 

 may well raise the point that if, as in avitaminosis, the causal link 

 between the physiological disturbance and the effect on enzyme sys- 

 tems is unquestioned, then surely there is a good case for assuming the 

 same link between normal physiology and enzyme systems." 



"The study of endocrines has always been one of the most active 

 fields of physiological investigation, and it is of interest to inquire 

 to what extent hormones can be related to enzyme phenomena. 

 Until quite recently, hormones were held up as notable excep- 

 tions to the rule that substances which act at high dilutions must 

 be enzymes or parts of enzymes, or must specifically affect some 

 enzyme system. Recent research, however, fails to confirm the 

 hormones as exceptions to the enzyme-trace substance thesis — the 

 epoch-making discovery of Cori and his group 14 that one of the 

 hormones of the anterior pitituary inhibits the action of hexo- 

 kinase, and that this inhibition, in turn, is released by insulin. 

 We have here a clear blueprint for the way in which hormone 

 antagonism can be effected. A key enzyme system which controls 

 some metabolic process can be regulated by a set of hormones, 

 one of which inhibits, while the other releases the inhibition. 

 All students of endocrinology have long been aware that hor- 

 mones regulate metabolic processes, and it is not surprising to find 

 in one instance, at any rate, that the regulation operates at the 



