PHYSIOLOGICAL FUNCTION FROM THE 

 STANDPOINT OF ENZYME CHEMISTRY 



By D. E. Green 



Departments of Medicine and Biochemistry, College of Physicians and Surgeons, 

 Coluinbia University, New York, N. Y. 



It is a curious fact tliat, although there is general recognition and 

 agreement that the cell is a chemical system, none the less the full im- 

 plications of this truism have yet to be appreciated in some fields of 

 physiological investigation. Perhaps the explanation is to be found in 

 the preoccupation of biochemistry, until very recently, with problems 

 of the structure of cellular constituents and with their estimation. 

 Classical biochemistry represented to the physiologist the extension of 

 histology to the chemical field. The study of what we may call chem- 

 ical morphology was hardly calculated to attract physiologists or to 

 arouse their interest in the chemical basis of physiological function. 

 However, the interest of biochemistry has been shifting gradually from 

 the purely structural problems to the dynamic chemical events of the 

 cell. Our present knowledge of the chemical mechanisms of the cell 

 has grown sufficiently for it to be ignored no longer by those who are 

 concerned with the study of physiological function. 



We may conceive of the cell as a chemical factory in which literally 

 thousands of chemical reactions take place, cheek by jowl, without 

 mutual interference. Some of these reactions are concerned in the syn- 

 thesis of structural components of the cell and others in providing 

 chemical energy for carrying on the activities of the cell. Practically 

 without exception, these reactions do not proceed spontaneously. They 

 require the presence of protein catalysts, which we call enzymes. Each 

 enzyme is distinct, chemically, from all the others, and is uniquely 

 specialized for its particular catalysis. If this picture of the cell is 

 correct, then it follows that all dynamic activities including physiolog- 

 ical function must be reducible to terms of enzyme chemistry. In other 

 words, physiological function and enzyme chemistry are two sides of 

 the same coin. I hope, in the short time at my disposal, to marshal 

 the available evidence which justifies this interpretation. 



In the syndromes of avitaminosis, we observe profound morphological 

 and physiological abnormalities. The recognizable signs of each of the 

 vitamin deficiencies are too well known to be discussed here. The point 



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