VOL. 12 (1953) BIOCHIMICA ET BIOPHYSICA ACTA 181 



ON THE COMPOSITION OF THE SOLUBLE NITROGEN FRACTION 



IN THE PEA PLANT AND ALDER 



by 



ARTTURI I. VIRTANEN and J. K. MIETTINEN 

 Biochemical Institute, Helsinki {Finland) 



Development of new methods of analysis, especially paper chromatography, in the 

 recent years has made it possible to study in greater detail than before the soluble ni- 

 trogen compounds of plants. This "non-protein" nitrogen fraction has drawn particular 

 attention because it is obviously the source of protein synthesis and also contains de- 

 composition products of proteins and amino acids. So far especially the amino acid 

 composition of the soluble nitrogen fraction has been examined with certain plants. 

 Among the investigators working in this field should be mentioned in particular Dent, 

 Steward and collaborators^' 2' ^'* Hunt^, Synge^, Hulme and Arthington^. Steward 

 AND Thompson^ have reviewed the literature up to the end of 1949. 



The investigations so far have many-sidedly revealed which amino acids are in 

 general found free in higher plants. The amino acids present generally in proteins, e.g. 

 aspartic and glutamic acids and their amides, alanine, valine, leucines, phenylalanine, 

 tyrosine, serine, threonine, proline, lysine, arginine, have been found as common free 

 amino acids in higher plants. Certain new amino acids, unknown in proteins, have been 

 detected by chromatographic methods free in higher plants. Steward et al.^ identi- 

 fied and isolated y-amino butyric acid (y-AB) first from potato and later it has been 

 found to be a common amino acid in plants. Piperidine-2-carboxylic acid has been 

 isolated from Trifolmm repens (Morrison^' ^), from seeds of bean^^, from apple'', and 

 growing pea^^. y-Methylene glutamine, a new amide, has been isolated from Arachis 

 hypogaea (Done and Fowden^^'^^). In this laboratory homoserine has recently been 

 isolated from growing pea (Miettinen et al.^'^). 



The occurrence of some unusual amino acids in high concentration in certain plants 



In this laboratory the composition of the soluble nitrogen fraction especially in 

 different tissues of leguminous plants and alder has been studied during the last two 

 years. These plants receive their nitrogen nutrition from the atmosphere by the action 

 of their root nodules. However, they are also able to grow on the nitrogen compounds 

 taken up by their roots. It is therefore of great interest to examine how the composition 

 of the soluble nitrogen fraction is affected by the nature of the nitrogen nutrition. We 

 shall revert to this question in another connection. The leguminous plants are also the 

 protein-richest of all plants, hence, the powerful protein synthesis taking place in them 

 is enough to arouse special interest in their soluble nitrogen fraction. 



The composition of the soluble nitrogen fraction differs to a surprising extent in 

 alder (Alnus glutinosa and incana) and pea [Pisum sativum). In pea the amount of 

 References p. i8y. 



