VIII] THE PROTEINS AND PROTEASES 127 



Crystalline globulins have also been isolated from the following 

 seeds but have as yet no distinctive names : Flax (Linum usitatissimum), 

 Squash {Cucurhita ma^ctwa), Castor-oil Bean {Ricinus communis), Qoconwi 

 (Cocos nucifera), Cotton-seed {Gossypium herhaceum). Sunflower {Heli- 

 anthus annuus), Radish {Raphanus sativus), Peanut {Arachis hypojaea). 

 Rape (Br-assica campestris) and Mustard {Brassica alba). 



It will be seen that the majority of reserve proteins of seeds are 

 globulins. It is probable that native and artificial crystalline proteins 

 are identical in many cases. 



Prolamins. These proteins are characterized by the fact that they 

 are insoluble in water and dilute saline solutions, but are soluble in 

 70-90 "/o alcohol. Such proteins are peculiar to plants, and are formed 

 to a considerable extent in the seeds of cereals. The principal ones 

 which have been isolated are : 



Gliadin found in the seeds of Wheat {Triticum vulgare). 



„ „ „ Rye {Secale cer-eale). 



Hordein „ „ Barley {Hordeum vulgare). 



Zein „ ,, Maize {Zea Mays). 



The properties of the gliadins are demonstrated in Expts. 128, 129, 

 130 and 131. 



Glutelins. The proteins of this group are insoluble in water, dilute 

 saline solutions and in alcohol, but they are soluble in dilute alkalies. 

 Glutenin of wheat is the only well-characterized member of this class 

 which has so far been isolated, though other cereals most probably 

 contain similar proteins. A protein of this nature has also been obtained 

 from seeds of Rice (Oryza sativa). The properties of the glutelins are 

 demonstrated in Expts. 128, 129 and 131. 



Nucleoproteins, Though these proteins probably form constituents 

 of all cells, the only members of the class investigated are those of the 

 wheat embryo. This has been possible since nuclei form a large pro- 

 portion of the tissue of the embryo. They may be regarded as protein 

 salts of nucleic acid, i.e. protein nucleates. On hydrolysis with acids or 

 enzymes they split up into various proteins and nucleic acid. The 

 nucleoproteins are also connected with the purins (see p. 164). 



Metaproteins. These are hydrolytic products of albumins and glo- 

 bulins formed by the action of water or dilute acid or alkali. They 

 are insoluble in water, strong mineral acids and all solutions of neutral 

 salts, but are soluble in dilute acids and alkalies in the absence of any 

 large amount of neutral salt. 



