SERINE. 145 



it sublimes. Its solubility in water is 1.5:100; at 20 in aqueous so- 

 lution () D +6.53 and in 20 per cent hydrochloric acid+14.1. It gives 

 a copper salt crystallizing in needles. 



CH 2 (OH) 



Z-Serine (a-amino-/3-oxypropionic acid), C 3 H 7 N03 = CH(NH 2 ), was 



COOH 



obtained by FISCHER and his collaborators as a cleavage product of 

 several proteins, generally only in small quantities. The largest quan- 

 tity, 6.6 per cent, was obtained by FISCHER and SKITA from sericine; 

 KOSSEL and DAKIN l obtained a still larger amount from salmine, namely 

 7.8 per cent. The racemic serine is the one generally obtained. From 

 fibroin FISCHER 2 obtained a mixture of active and inactive serine anhy- 

 dride from which he finally prepared Z-serine by hydrolysis. Serine has 

 also been found by G. EMBDEN and TACHAU 3 in fresh perspiration. 



Synthetically cW-serine has been prepared by FISCHER and LEUCHS 

 from ammonia, hydrocyanic acid and glycol aldehyde, and also in other 

 ways by others. 4 FISCHER and JACOBS 5 have prepared Z-serine from 

 d-/-serine by the preparation of the alkaloid salt of the p-nitro-benzoyl 

 combination. On reduction serine is transformed into alanine, and on 

 oxidation with nitrous acid it yields glyceric acid. The relation of serine 

 to alanine, lactic acid and glyceric acid is evident from the following for- 

 mulae: 



CH 2 (OH) CH 3 CH 3 CH 2 (OH) 

 CH(NH 2 ) CH(NH 2 ) CH(OH) CH(OH) 

 COOH COOH COOH COOH 



Serine Alanine Lactic acid Glyceric acid 



The Z-serine crystallizes in thin leaves or crusts. It is rather readily 

 soluble in water; the d-Z-serine is soluble in 23 parts water at 20 C. 

 The solution of /-serine has a sweet taste with an insipid after taste. 

 The specific rotation in aqueous solution at 20 C. is (a) D = 6.83 

 and the hydrochloric acid solution at 25 C. is (a) D = + 14.45. The 

 /3-napthalene-sulpho-serine melts at 220 C. when anhydrous. The 

 Z-serine anhydride, which is identical with that obtained from fibroin, 

 forms thin, colorless needles which melt at 247 with decomposition. 

 Its specific rotation in aqueous solution at 25 C. (a) D = 67.46. 



1 Fischer and Skita, Zeitschr. f. physiol. Chem., 35; Kossel and Dakin, ibid., 41. 



2 Ber. d. d. chem. Gesellsch., 40. 



3 Bioch. Zeitschr., 28. 



4 Fischer and Leuchs, Ber. d. d. chem. Gesellsch, 35; Erlenmeyer and Stoop, ibid., 

 35; Leuchs and Geiger, ibid., 39. 



5 Ber. d. d. chem. Gesellsch., 39. 



