8o THE VEGETABLE PROTEINS 



of the character of glutelins are widely distributed among the different 

 seeds there is no conclusive evidence that this is in fact so. 

 The only well-defined glutelins are thus : 



Glutenin found in the seeds of Wheat, Triticum vulgar e (366). 



and 

 Oryzenin found in the seeds of Rice, Oryza saliva (439). 



(*/) Prolamins. 



Alcohol-soluble proteins were among the first recognised in seeds, 

 having been described as early as 1805 by Einhof as occurring in the 

 seeds of rye (105) and barley (106). Taddei (537) found, in 1819, that 

 a part of the gluten of wheat was soluble in alcohol, and Gorham (135) 

 reported in 1821 a similar protein, which he called zein, in the seeds 

 of maize. Kreusler (21 1) in 1869 found in the oat-kernel an alcohol- 

 soluble protein, and the writer later found that the seeds of sorghum, 

 Andropogon sorghum (not published), also contain a considerable 

 quantity of such protein. Rosenheim and Kajiura (439) have found 

 that the seeds of rice are free from any protein soluble in alcohol. 

 Alcohol-soluble proteins have thus been found in the seeds of all 

 the cereals that have been examined with the exception of rice, but 

 have never been found in the seeds of any other family of plants. 



The group of alcohol-soluble proteins deserves a definite name, for 

 it is one of the best characterised groups yet found in either plants or 

 animals. It has recently been proposed to call these proteins " gliadins," 

 but as this name has been used to designate a definite protein obtained 

 from wheat, a more distinctive name should be adopted. The writer 

 has proposed (319) to call this group "prolamins," for all its members, 

 which have thus far been hydrolysed, yield a relatively large quantity 

 of both proline and amide nitrogen. The prolamins are characterised 

 by their solubility in alcohol of from 70 to 90 per cent. They are 

 nearly or wholly insoluble in water, but their salts with acids or 

 alkalies dissolve freely therein. They yield much glutaminic acid, 

 proline and ammonia, and, as Kossel and Kutscher (205) have shown, 

 small amounts of arginine and histidine and no lysine, 



The prolamin of wheat, Triticum vulgare, was named gliadin by 

 Taddei (507). Ritthausen (409) concluded that the alcohol-soluble 

 protein of wheat consisted of three distinct proteins, gliadin, mucedin 

 and gluten-fibrin, but subsequent investigations have not supported 

 this view (cf. 3 1 7). The prolamin of rye, Secale vulgar e, is also known 

 as gliadin, for no positive difference has yet been established between 

 it and the gliadin of wheat (304, 347). The prolamin of maize was 



