iH) A. I. \IRTANEN, J. K. MIETTINEN VOL. 12 (ltj53) 



hydrolysis of tlie fraction but have hitherto not been met in proteins. It has been shown 

 liy GoTTSCHAi.K AND Partridge^^ that in the reaction between a-amino acids and 

 reducing sugars the reactivity of the amino group increases as its distance from the carb- 

 oxyl grou]) increases. j8- and y-amino acids are, therefore, more inclined than a-amino 

 acids to comjilex-formation w^th sugars. In fact we have demonstrated paper chromato- 

 grajihically by using ammoniacal silver nitrate^^ and Chapman-McFarlane^^ reagents 

 that the "peptide" fraction contains strongly reducing compounds resembling those for- 

 med b\- sugars and amino compounds. 



'I'he nature of compounds in this fraction is still obscure. Xo fractionation of the 

 "pejitide" fraction with electric current was obtained at pH 7 in silica-jelly ionophoresis 

 by the method of CoNSDEN cf al.'^^. Since it was also found that the "peptides'" are not 

 l)ound to the cation exchange resin Amberlite IR-105 (H+) it is evident that their end- 

 amino groups are blocked. 



When examining the soluble nitrogen comj)ounds of rye grass Synge^ came to 

 investigate the nature of nitrogen compounds in many respects similar to those con- 

 tained in our "})eptide" fraction. He discussed the nature of these nitrogen compounds, 

 considering it {possible that they are compounds of amino acids and sugars, acyl amino 

 acids, or cyclopeptides. According to our findings the presence of acyl amino acids is 

 unlikely in our fraction. The chemical nature of the compounds contained in the "peptide" 

 fraction isolated bv i-is is under more detailed studv-* 



SUMMARY 



Great diticrences have been observed in tlie composition <j1 the free amino acids of alder and 

 pea. Citrulline is the predominating free amino acid in alder, whereas it is completely absent from 

 pea. On the other hand, amides, which are quantitati\ely dominant in the soluble nitrogen fraction 

 of pea, are absent from the alder. Homoserine, which earlier has not been detected in higher plants, 

 has been identified and isolated from pea in crystalline form. Special attention has been paid to the 

 soluble fraction of pea containing bound amino acids. This fraction has been i.solated free from free 

 amino acids. On total hydrolysis, but not on mild hydrolysis, this "peptide" fraction yields the same 

 .imino acids as are met in free state in the pea plant, among them e.g. }'-amino butyric acid, /^-alanine, 

 and homoserine. The chemical nature of the nitrogen compounds in this fraction has been discussed. 



RESUMfi 



La composition en acides amines libres de I'aune est tres differente de celle du ])ois. Chez I'aune, 

 la citrulline est I'acide amine libre le plus ab(jndant, tdors (|u'elle est absente chez le pois. Au contraire, 

 Ics amides, qui dominent cpiantitativcment dans la fraction soluble de I'azote du pois, sont abscntes 

 chez I'aune. L'homoserine, (jui n'avjiit pas ete trouvee jusc|u'a present chez des plantcs superieures, 

 a ete identifiec ct isolce sous forme cristalline a ])artir du j)ois. Nous avons etudie i)articulierement la 

 fraction soluble du ]XMS(|uirenfermedesacidesamineslies.Cettefractiona etc isolce et debarrassee des 

 acides annnes libres. Apres hydrolyse totale, mais non apres hydrolyse menagec, la fraction "pepti- 

 diquc" rcnferme les acides amines qu'on trouve a I'ctat libre chez le pois, parmi le-squcls par example 

 I'acide y-aminobutyri(jue, la /i'-alaninc et riiomosc'rinc. l.a nature (■liimi(|ue des composes azotes de 

 cette fraction est envisagee. 



Ad(fi/ioii tit Ihc fyroof. I'^videncc has bi'en found that this fraction contains compounds of amino 

 acids with sugars. Througli the infhuMicc of proteolytic enzymes (pepsine | trypsine) no amino acids 

 were split from the original nor mildl\- I K'i-liydrolyzcd "pcptide"-fractinn. Thus, llu ic is no proof for 

 peptide bonds so far. 



Refei'oiccs p. i8y . 



