Cellular oxidations and the syntheiss of amino-acids and amides in plants 



E. W. Yemm. The relation between the two amides, glutamine and asparagine, in 

 the metabolism of barley plants has been discussed in an earlier account of our work. 

 In general asparagine accumulates in the cell under conditions of carbohydrate 

 shortage and proteolysis; this seems to hold for root tissues. Under conditions norm- 

 ally obtaining during the growth of the plant glutamine appears to be much more 

 closely related to the metabolism of proteins. 



The estimates of total insoluble-N (protein) in roots and yeast were usually 

 obtained after extraction with alcohol and water. 



0. Maalee. Is it possible, in your system, to follow synthesis of amino-acids, peptides, 

 and protein long enough to observe an equilibrium between the concentrations of 

 low- and high-molecular-weight compounds; if so, can it be estimated what fraction 

 of amino-N, at equilibrium, is in the pool of low-molecular-weight substrates for 

 protein synthesis ? 



E. W. Yemm. Equilibrium conditions between the nitrogenous constituents do not 

 appear to be established in our experiments; but we have very little knowledge of 

 the nature or amount of peptides present in the cells. 



W. S. Reith. In the meristematic cell, the amount of peptide nitrogen and amino-acid 

 nitrogen is very small in comparison with the protein nitrogen. 



B. F. Folkes. The low level of soluble nitrogen other than glutamic acid, glutamine 

 or alanine, indicates the low level of other amino-acids and peptides in the cell. 

 It seems that the low level of these products limits the rate of protein synthesis. 



L. Rinaldini. The rise in GSH might be connected with the oxygen uptake in view o 

 the respiratory mechanism recently found in plants by Mapson, where GSH acts 

 as a hydrogen carrier between dehydrogenases and ascorbic acid, which in turn 

 reacts with molecular oxygen. 



E. W. Yemm. I fully agree that glutathione may be active in other processes of cellular 

 metabolism. In addition to transpeptidations and oxidation-reductions it may have 

 a regulating action on -SH enzyme systems. 



E. Ambrose. With regard to the transpeptidation and template theories of protein 

 synthesis, if the transpeptidation theory is correct, there is a pool of peptides in 

 dynamic equilibrium within the cells, which is increased in concentration by feeding 

 with the source of nitrogen ; this increase may be to some extent independent of 

 other cellular processes. If on the other hand we are dealing with a nucleic acid 

 template, there might be a close correspondence between the concentration of pep- 

 tides and of nucleic acids within the cell. Has a relationship been found between the 

 peptides and nucleic acid concentrations within yeast cells ? 



E. W. Yemm. We have not yet studied the change of nucleic acids during protein 

 synthesis in food yeast; as far as I am aware no data have been published. Judging 

 from Gale's work with bacteria and Hokin's with animal tissues, substantial synthesis 

 of proteins may occur in cells without appreciate changes in the amount of nucleic 

 acids. 



J. F. Danielli. The fact that more isotopic nitrogen appears in the proteins than can 

 be accounted for by net synthesis may mean that individual amino-acids or peptides 



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