28 E. S. EDIE 



Digestion in cc. 

 of Njl^i nitrogen 



21. (a) 15 cc. trypsin, 10 cc. 15 % alcohol I , ^ ^ .,„. „ , „ , 



a( IK ^ • lA / [ kept at 37° C. for 3 hours 



(0) 15 cc. trypsin, 10 cc water ) 



2 cc of (a), 40 cc 0-5 % Na^COa 16-3 



2 cc of (6), 40 cc 0-6 % NajCOa 16-2 



1 g. fibrin. Digestion 2-75 hours. 



No destruction whatever of the trypsin is caused by the action of 6 % 

 alcohol, although the digestive action of the enzyme is reduced to 30 % or 

 less of the normal amount by the presence of this proportion of alcohol. 



A solid substrarte such as fibrin might be rendered less digestible by pro- 

 longed treatment with concentrated alcohol, owing to the hardening thus 

 brought about. Alcohol of under 30 %, however, could hardly be supposed 

 to have such an effect, and a few experiments showed that after treatment 

 with dilute alcohol fibrin was no less digestible by trypsin than previously. 



Digestion in cc. 

 of NIIQ nitrogen 



22. (1) Fibrin + 10% alcohol) , , , .,^, ^ , ., . 



/ > T?-u • / \ kept at 37° C. for 3 hours 



(2) Fibnn + water | 



1 cc trypsin, 40 cc 0-5 % NaaCOg, 1 g. fibrin (1) ... 19-3 



1 cc trypsin, 40 cc 0-5 % NaaCOg, 1 g. fibrin (2) 18-1 



Digestion 2*5 hours. 



23. (1) Fibrin + 10 %alcohon , ..nont ^a^. 



(2) Fibrin + 10 % alcohol [ ^'^' ^' ^^ ^- ^""^ ^^ ^""'^ 



1 cc trypsin, 40 cc 0-5 % NajCOg, 1 g. fibrin (1) 22-9 



1 c.tj. trypsin, 40 cc. 0-5 % NaaCOs, 1 g. fibrin (2) 20-2 



Digestion 3 hours. 



The fibrin which was to be treated with alcohol in these experiments was 

 first washed with alcohol in order to remove any adherent moisture. It will 

 be seen that after treatment with 10 % alcohol fibrin is apparently slightly 

 more readily attacked by trypsin than previously. 



The action of trypsin on fibrin and on caseinogen is affected by dilute 

 alcohol to such different degrees that it is reasonable to suppose either that 

 there are two enzymes concerned in the digestion of these proteins or that 

 different groups of the same enzyme molecule take part in the hydrolysis of the 

 different proteins. In the latter case the groups which digest fibrin are very 

 much more easily inhibited by alcohol than the groups which digest casein- 

 ogen. 



The theory that different side chains in the molecule of an enzyme are 

 responsible for different functions is used to explain the zymoid modification 

 of enzymes. Some observers also, for example, Nencki and Sieber [1901], 

 hold that the behaviour of pepsin and rennin under varying conditions can 

 best be explained on the theory that only one enzyme is concerned here, 

 with different side chains responsible for the proteolytic and milk coagulating 

 functions. Vernon [1903, 1] also considers this probable in the case of the 

 milk coagulating and proteolytic actions of trypsin. 



Hitherto it has apparently been assumed that one enzyme "trypsin" is 

 responsible for the digestion of fibrin and caseinogen by pancreatic extracts. 



(224) 



