AMINO ACIDS 



Amino acids are generally recognized primarily in 

 their role as structural units of proteins. The fact 

 that amino acids may have additional important 

 roles may not always be fully appreciated. There are 

 already more non-protein than protein amino acids 

 known, for example, and the ratio of non-protein to 

 protein amino acids will increase as new amino acids 

 are discovered (Fig. 6-1). Numerous ninhydrin posi- 

 tive substances, yet uncharacterized, are known. 

 Most, if not all, of the protein amino acids are of 

 little taxonomic value by virtue of their cosmopoli- 

 tan distribution! while the non-protein acids are 



1 Eventually, however, as indicated previously, the struc- 

 tural sequence of protein amino acids may prove to be among the 

 ultimate phylogenetic criteria. 



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