WP 



Amino acid 



"^^ synthesis 



Among the first compounds found to be labeled by pho- 

 tosynthesis of C^*02 in algae were alanine, aspartic acid, and 

 several other amino acids (11). These compounds were 

 slowly labeled even in the dark when algae were exposed 

 to C^^02. They and malic acid were much more rapidly 

 labeled if the algae were photosynthesizing, or had been 

 photosynthesizing, just prior to the moment of addition of 

 C^^02. We recognized that these amino acids were therefore 

 products of photosynthetic reduction of CO2, even though 

 they could also become labeled by reversible respiratory re- 

 actions. Accelerated incorporation of C^^ into amino acids 

 in higher plants during photosynthesis has been noted in 

 this laboratory (23,24) and in many others (25-28). Nichi- 

 porovich (25) has presented and reviewed evidence that syn- 

 thesis of proteins in the chloroplasts of higher plants is 

 greatly accelerated during photosynthesis. This accelerated 

 protein synthesis appears to occur directly from the inter- 

 mediates of photosynthetic carbon reduction, since the pro- 

 teins were labeled when C^^02 was used but not when C^'*- 

 labeled carbohydrate was administered. Photosynthetically 

 accelerated synthesis of protein containing N^^ was also ob- 



29 



