152 THE PROTEIN SUBSTANCES. 



was first found by E. SCHULZE and BARBIERI l in etiolated lupin sprouts. 

 It is produced in the acid cleavage of protein substances in quantities 

 rarely above 5-6 per cent. It has been prepared synthetically in several 

 ways by ERLENMEYER, JR., SORENSEN and E. FISCHER, WHEELER and 



HOFFMAN. 2 



The Z-phenylalanine crystallizes in small, shining leaves or fine needles 

 which are rather difficultly soluble in cold water but readily soluble in 

 hot water. The solution has a faint bitter taste. A 5-per cent solution 

 acidified with hydrochloric acid or sulphuric acid is precipitated by 

 phosphotungstic acid, while a more dilute solution is not precipitated. 

 On putrefaction, phenylalanine yields phenylacetic acid. On heat- 

 ing with potassium dichromate and sulphuric acid (25 per cent) an odor 

 of phenylacetaldehyde is produced and benzoic acid is formed. In 

 aqueous solution it has a rotation of (a) D = 35.1. The phenyliso- 

 cyanate-1-phenylalanine melts at about 182 C. 



Z-Tyrosine (p-oxyphenyl-a-aminopropionic acid), 



C 6 H 4 (OH) 



COOH 



is produced from most protein substances under the same conditions 

 as leucine, which it habitually accompanies. The largest quantity of 

 tyrosine obtained from animal proteins was about 10-13 per cent (see 

 tables, pages 106, 107, 115 and 125): In gelatin and a few keratins 

 tyrosine is absent. It is especially found with leucine, in large quantities, 

 in old cheese (Tvpos), from which it derives its name. Tyrosine has not 

 been found with certainty in perfectly fresh organs. It occurs in the 

 intestine during the digestion of protein substances, and it has about 

 the same physiological and pathological importance as leucine. 



Tyrosine was prepared by ERLENMEYER and LIPP from p-amino- 

 phenylalanine by the action of nitrous acid, and according to another 

 method by ERLENMEYER and HALSEY. S On fusing with caustic alkali 

 it yields p-oxybenzoic acid, acetic acid, and ammonia. On putrefaction 

 it may yield oxyphenylethylamine, oxyphenylpropionic acid, oxyphenyl- 

 acetic acid, p-cresol and phenol. 



1 Ber. d. d. chem. Gesellsch., 14, and Zeitschr. f. physiol. Chem., 12. 



2 Erlenmeyer, Annal. d. Chem. u. Pharm., 275; Sorensen, Zeitschr. f. physiol. 

 Chem., 44; E. Fischer, Ber. d. d. chem. Gesellsch., 37; Wheeler and Hoffman, Amer. 

 Chem. Journ., 45. 



3 Erlenmeyer and Lipp, Ber. d. d. chem. Gesellsch., 15; Erlenmeyer and Halsey, 

 ibid., 30. 



