90 THE VEGETABLE PROTEINS 



of conglutin were recovered. According to Mack (250, 251) the seeds 

 of the yellow lupine contain an enzyme which at neutral or acid 

 reaction attacks the protein, and it is probable that the large loss of 

 conglutin was due to the action of this enzyme. 



As the formation of proteose would almost certainly accompany 

 the formation of diffusible products which do not give protein reac- 

 tions, the proteoses found in the extracts cannot be considered to be 

 original constituents of the seeds until more convincing evidence is 

 obtained than any as yet given. 



(b) Peptones. 



The facts which lead to the uncertainties respecting the pre-exis- 

 tence of proteoses in seeds apply also to the peptones. The most 

 elaborate investigation of this subject has been made by Mack (251), 

 who obtained peptone from lupine-seeds under conditions which he 

 thought entirely excluded its formation by enzyme action. He 

 worked with very large quantities of seeds and employed Siegfried's 

 method of isolating and purifying peptones by means of ferric-am- 

 monium alum. The several products obtained had a nearly constant 

 composition corresponding to the formula C 32 H 56 N 8 O 6 , while the 

 barium salt contained an amount of barium in close accord with the 

 calculated. When hydrolysed with hydrochloric acid this peptone 

 yielded lysine, arginine and glutaminic acid. 



By artificially digesting vegetable proteins with pepsin or trypsin, 

 proteoses and peptones have been obtained by Chittenden (68), 

 Chittenden and Hartwell (69, 70), Chittenden and Mendel (71), and 

 Chittenden and Smith (73). 



(c) Peptides. 



Only two well-characterised peptides have thus far been obtained 

 from seed proteins. The first of these was a dipeptide of proline and 

 phenylalanine, which Osborne and Clapp (339) isolated from the de- 

 composition products of gliadin which had been decomposed by boil- 

 ing with 25 per cent, sulphuric acid for many hours. This peptide 

 was obtained in beautiful mother-of-pearl crystals of definite form, and 

 yielded a copper salt, the crystals of which were so large and well 

 formed that the measurement of their angles served to definitely 

 characterise the substance. By hydrolysis in a sealed tube with strong 

 hydrochloric acid it yielded proline and phenylalanine in molecular 



