146 THE PROTEIN SUBSTANCES. 



Isoserine (/3-amino-a-oxypropionic acid) has been prepared by ELLINGER 

 from diamino-propionic hydrobromide and silver nitrite, and by NEUBERG and 

 SILBERMANN from the hydrochloric acid combination of diamino-propionic acid. 

 Other syntheses have been made by NEUBERG and MAYER and by NEUBERG 

 and AscHER. 1 



COOH 

 /-Aspartic acid (aminosuccinic acid), C4H7N04 = A TJ , has been 



COOH 



obtained on the cleavage of protein substances by proteolytic enzymes as 

 well as by boiling them with dilute mineral acids in comparatively small 

 quantities. This acid also occurs in secretions of sea-snails (HENZE 2 ) 

 and is very widely diffused in the vegetable kingdom as the amide 

 Asparagine (aminosuccinic-acid amide), which seems to be of the 

 greatest importance in the development and formation of the proteins 

 in plants. d-Z-Aspartic acid has been prepared synthetically from fumaric 

 acid and alcoholic ammonia. On putrefaction of aspartic acid, propionic 

 acid and succinic acid are formed. 



Z-Aspartic acid dissolves in 256 parts water at 10 C. and in 18.6 parts 

 boiling water, and on cooling crystallizes as rhombic prisms, and its 

 4 per cent solution acidified with HC1 has the rotation (a) D = +25.7; 

 in alkaMne solution the acid is levo-rotatory. It forms with copper 

 oxide a crystalline compound which is soluble in boiling-hot w r ater and 

 nearly insoluble in cold water, and w r hich may be used in the prepara- 

 tion of the pure acid from a mixture with other bodies. 



The benzoyl-Z-aspartic acid melts at 184-185. For identification 

 we make use of the analysis of the free acid and the copper salt, as well 

 as of the specific rotation. 



COOH, 

 CH(NH 2 ) 



d-Glutamic acid (a-aminoglutaric acid), C5H9N04 = CH2 , is 



CH 2 

 COOH 



obtained from the protein substances under the same conditions as the 

 other monamino-acids (see tables on pages 106, 107, 115 and 125) and 

 from the peptones (SIEGFRIED). It is absent in the protamines and in the 

 varieties of silk, it occurs only in small amounts w r ith the exception of spi- 

 der's web. HLASIWETZ and HABERMANN obtained 29 per cent from casein 

 by cleavage with hydrochloric acid, while KUTSCHER could obtain only 

 1.8 per cent glutamic acid by cleavage with sulphuric acid. Other 



1 Ellinger, Ber. d. d. chem. Gesellsch., 37; Neuberg and Silbermann, ibid., 37J 

 Neuberg and Mayer, Biochem., Zeitschr 3; Neuberg and Ascher, ibid., 6. 



2 Ber. d. d. chem. Gesellsch., 34. 



