ENZYMES AS SYNTHETIC AGENTS 485 



Considerable quantities of nitrogen were given off by these 

 chloroformed plants in the presence of asparagin, and there 

 seems little doubt that this was evolved as the result of reduction 

 of nitrate by the reductase present in the tissue. 



There is no reason at present to anticipate that enzymes play 

 a part in the stages that follow upon the formation of nitrites 

 until at length the "amino" linkage, NH 2 , is reached. The 

 intervening compounds are likely to be so highly reactive that 

 the successive changes are probably instantaneous and there 

 seems no necessity to assume the intervention of a catalyst. 



The suggestions of Bach and Baudisch previously mentioned 

 raise the question whether the synthesis of proteins can be 

 considered independently of carbohydrate metabolism. Alde- 

 hydes play a part in the suggested reactions, and it is during 

 photosynthesis that such bodies are likely to be formed in the 

 plant. Moreover, recent work in another direction has drawn 

 attention to the possibility of the intervention of enzymes in the 

 passage from the carbohydrate to the amino-acid. This work 

 will be considered in the succeeding section. 



2. Relation of Carbohydrate Metabolism to Protein 



Synthesis 



In the preceding section reference was made to a possible 

 inter-relation between the metabolism of carbohydrates and 

 protein synthesis. 



The result of the brilliant synthesis of proteins from amino- 

 acids carried out in the chemical laboratory by Emil Fischer and 

 others l has been to focus attention upon the amino-acids as the 

 primary bodies from which must start the synthesis of proteins 

 within the organism. In the plant these amino-acids have to be 

 constructed. 



We have seen that the nitrogen, however supplied, is 

 probably brought gradually to the NH 2 grouping, but we have 

 still to ascertain whence the organic acid or aldehyde is 

 obtained, with which this NH 2 grouping may be linked. In this 

 connection the recent work of Dakin and Dudley upon the 

 activities of an enzyme they have termed glyoxalase, may have 

 great significance for students of plant metabolism. 



1 See R. H. Plimmer, "Chemical Constitution of the Proteins," I. and II. 

 Biochem. Monographs, pub. Longmans, Green & Co., for a valuable summary of 

 recent work. 



