46 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



Hopkins and Savory's thorough investigation of the Bence- Jones 

 protein in 1911, in which they showed that its peculiar physical pro- 

 perties were due to the conditions under which it was examined, and 

 that its chemical composition differed so distinctly from that of the 

 proteoses, brings this protein into the class of coagulable proteins as a 

 globulin. The Bence-Jones protein is characterised chemically by a 

 high content of the aromatic amino acids ; the combined values for 

 phenylalanine and tyrosine are higher than those for any other blood 

 or tissue protein. Both physically and chemically this protein seems 

 to stand in a class by itself. 



The Vegetable Proteins. 



The vegetable proteins show no great difference from the animal 

 proteins in regard to the number of amino acids which they contain in 

 their molecule. The most noticeable features are their high content in 

 glutamic acid and in arginine. Their ammonia content is also high. 

 This is probably connected with the large amount of the dibasic 

 glutamic acid and is in harmony with the occurrence of asparagine and 

 glutaminean growing seedlings. 



Albumins. 



Only two vegetable albumins have so far been analysed, the 

 legumelin of the pea and the leucosin of wheat. The resemblance in 

 their composition extends not only to the general proportions of the 

 amino acids, but also to the quantity isolated. Leucosin occurs in 

 the embryo of wheat ; it is not possible to locate legumelin in any 

 particular part of the seed, but, from analogy, it may be supposed that 

 both these proteins are constituents of the physiologically active tissues 

 rather than a constituent of the reserve 'food-stuff for the embryo. 

 Legumelin is quite different in composition from legumin and 

 vicilin, two other proteins contained in the pea. These albumins show 

 a resemblance in their composition to the animal albumins. 



