W. YEMM 



CONCLUSION 



With regard to the wider problems of protein synthesis, the following conclusions 

 may be drawn from the data so far obtained. 



( i ) A rapid formation of glutamic acid and glutamine, which occurs in the first 

 stages of nitrogen assimilation in yeast and in barley tissues, is closely coupled with 

 carbohydrate metabolism and the exergonic reactions of cellular oxidations. 



(2) The primary synthesis of amino and amide groups may be linked with the 

 formation of other amino-acids and of peptides by means of enzymic systems which 

 promote transamination and transamidation in the cell. 



(3) Some support is therefore given to the hypothesis of peptide-bond formation 

 by transamidation and transpeptidation, but as yet very little is known of the speci- 

 ficity or course of peptide synthesis in living cells. 



(4) It seems possible from this and other evidence that the action of specific 

 surfaces, visualized in the 'template' hypothesis, operates at a later phase of protein 

 synthesis by affecting the folding and cross-bonding of polypeptide structures. The 

 role of nucleic acids in protein formation may be in this stage, rather than in the 

 direct synthesis of peptide bonds. 



The experimental work was carried out in collaboration with my colleagues, 

 Dr. Folkes and Dr. Willis; their permission to present some hitherto unpublished 

 results is gratefully acknowledged. 



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