PROTEINS. 



105 



of the gluten. It is not definitely known whether glutelins occur 

 as constituents of all seeds. 



Prolamins (Alcohol-soluble Proteins). 



The term prolamin has been proposed by Osborne, for the group 

 of proteins formerly termed " alcohol-soluble proteins." The name 

 is very appropriate inasmuch as these proteins yield, upon hydroly- 

 sis, especially large amounts of proline and ammonia. The pro- 

 lamins are simple proteins which are insoluble in water, absolute 

 alcohol and other neutral solvents, but are soluble in 70 to 80 per 

 cent alcohol and in dilute acids and alkalis. They occur widely dis- 

 tributed, particularly in the vegetable kingdom. The only prolamins 

 yet described are the sein-oi maize, the hordein of barley, the gliadin 

 of wheat and rye and the bynin of malt. They yield relatively large 

 amounts of glutamic acid on hydrolysis but no lysin. The largest 



FIG. 34. 





EXCELSIN, THE PROTEIN OF THE BRAZIL NUT. 



(Drawn from crystals furnished by Dr. Thomas B. Osborne, New Haven, Conn.) 



percentage of glutamic acid (41.32 per cent) ever obtained as a 

 decomposition product of a protein substance has very recently been 

 obtained by Kleinschmitt from the hydrolysis of the prolamin 

 hordein. 1 This yield of glutamic acid is also the largest amount 

 of any single decomposition product yet obtained from any protein 

 except protamines. 



^p to this time the yield of 37-33 per cent obtained by Osborne and Harris 

 from gliadin, was the maximum yield. 



