CHEMICAL STRUCTURE AS A GUIDE TO THE 

 STUDY OF BIOCHEMICAL SYNTHESES* 



KONRAD BLOCH, Department of Chemistry, Harvard University, 



Cambridge, Massachusetts 



In the study of biochemical syntheses it would appear 

 reasonable to proceed on the premise that the mechanisms of 

 formation of tissue constituents are implicit in their chemical 

 constitution. Indeed, this line of thinking is responsible for the 

 many attempts to deduce biochemical pathways from typical 

 features of chemical structure and from the in vitro behavior of 

 organic molecules. It is a matter of fact, however, that past 

 efforts to decode the information which is provided by chemical 

 constitution have had only limited success. For example, the 

 discoveries of the role of acetate in steroid biogenesis, of succinic 

 acid and glycine in porphyrin formation, or of formate and 

 glycine as purine precursors were not at all what would have been 

 expected from the background of chemical or biochemical 

 knowledge. They have since been rationalized, but were hardly 

 predictable from any particular structural features of the end 

 products. Though the use of structural arguments to predict 

 biochemical pathways has been perhaps somewhat discredited 

 by its past record, the contribution which chemical theory can 



* The author is indebted to Dr. R. B. Clayton for valuable discussion of 

 the contents of this paper. 



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