v PLASTEINS 191 



Plasteines. Anti-albumids. Dysalbumose 



Kiihne 1 was the first to observe the formation of the so-called 

 anti-albumids. If that portion of a proteid which is not acted upon 

 by a prolonged digestion with pepsin-hydrochloric acid is subsequently 

 subjected to tryptic digestion, a delicate jelly separates out, the 'anti- 

 albumid coagulum,' which is also very slightly changed by trypsin. 

 This resisting anti-albumid is remarkable for containing a much higher 

 percentage of carbon than does ordinary albumin : Kiihne and Chitten- 

 den found from 57 to 58 per cent carbon ; it yields very little ty rosin 

 and much anti-peptone. 



Subsequently Okunew, 2 Lawrow, 3 Sawjalow, 4 and Kurajeff 5 found, 

 in Danilewsky's laboratory, a similar fraction on adding lycopodium 

 powder to a mixture of the products resulting from peptic digestion. 

 They called the body which separated out 'plastein,' and were of the 

 opinion that it had been regenerated out of the albumoses. Sawjalow 

 pointed out the resemblance between plastein and anti-albumid ; for 

 they are closely related, judging by their chemical composition. 

 Gelatine and keratine yield, however, no plastein or coagulose on 

 being digested (Okunew, Kurajeff). 



Pure gastric juice obtained by Pawlow's method, according to 

 Lawrow and Salaskin, 6 acts like rennet ; papayotin does the same, 

 according to Kurajeff. 7 Umber 8 noticed a similar fraction if ammonium 

 sulphate was present during peptic digestion. All these phenomena 

 are based evidently on the common factor that every proteolytic 

 enzyme possesses a rennet-like action. 



Kurajeff 9 recently prepared plastein by digesting crystallised egg- 

 albumin for three days with pepsin -r hydrochloric acid, and then 

 precipitating the plastein with a solution of rennet. To purify it he 

 dissolved the plastein in one-tenth normal NaOH solution, and pre- 

 cipitated it with HC1. The plastein obtained after three days' digestion 

 he called plastein A, while the plastein prepared similarly, but after 

 eighteen days' digestion, is called plastein B. In both cases the 

 amount of plastein was 7 '3 per cent of the dry residue of the products 



1 W. Kiihne and R. H. Chittenden, Zeitschr. f. Bid. 19. 159 (1883). 



2 Okunew, Dissertation, St. Petersburg, Malys Jahresber. f. Tierchemie, 1895, 

 p. 291. 



3 Lawrow, Dissertation, St. Petersburg, 1897, according to Sawjalow. 



4 W. W. Sawjalow, Pfluger's Arch. f. d. ges. Physiol. 85. 171 (1901). 



5 D. Kurajeff, Hofmeister's Beitrage, 1. 112 (1901). 



6 M. Lawrow and S. Salaskin, Zeitschr. f. physiol. Chem. 36. 277 (1902). 



7 D. Kurajeff, Hofmeistcrs Beitrage, 1. 121 (1901). 



8 F. Umber, Zeitschr. f. physiol. Chem. 25. 258 (1898). 



9 D. Kurajeff, Hofmeister's Beitrage, 4. 476 (1904). 



