ENZYMES. FERMENTATION 407 



VIII. Trypsin. 



Trypsin is the activated proteoclastic enzyme of the pancreas. It may be 

 prepared by extracting the minced gland with glycerin for 12-24 hours 

 and straining through muslin. The solution is diluted with 2-3 volumes 

 of water before use. 



An active solution of trypsin may also be prepared by treating the minced 

 pancreas with 3 times its weight of distilled water and an equal weight of 

 alcohol for 3 days at room temperature with occasional shaking. The solu- 

 tion is strained through muslin and filtered. To the filtrate i c.c. of con- 

 centrated hydrochloric acid per 1000 c.c. is added. A precipitate which forms 

 is allowed to settle and is filtered off. 



In preparing trypsin from the pancreas it is advisable to add a small 

 amount of the mucous membrane of the intestine so as to activate the enzyme 

 in case this is not done by contact with the intestine on removing the pancreas. 



Dry preparations of trypsin can be obtained by mincing the pancreas and 

 drying, or by precipitating with alcohol or evaporating the extracts. 



Numerous preparations of trypsin can be obtained commercially, e.g. 

 Benger's liquor pancreaticus, holadin of Messrs. Fairchild Bros. & Foster. 

 This latter preparation also contains lipase and diastase. 



Solution of fibrin or coagulated egg-white by the enzyme, as in 

 the case of pepsin, is the simplest means of investigating the presence 

 and action of trypsin. 



Four test tubes are filled with the following mixtures : 



(1) 5 c.c. of trypsin + 5 c.c. of *5 per cent. Na 2 CO 3 + a piece of 

 fibrin. 



(2) 5 c.c. of trypsin + 5 c.c. of water + a piece of fibrin. 



(3) 5 c - c - of trypsin 4- 5 c.c. of *iN HC1 + a piece of fibrin. 



(4) 5 c.c. of boiled trypsin + 5 c.c. of '5 per cent Na 2 CO 5 4- a 

 piece of fibrin. 



The four tubes are placed in a water-bath at 40. Only in the 

 first tube will any change be seen. In the tube containing hydro- 

 chloric acid the fibrin swells without dissolving. In the aqueous solu- 

 tion there is no visible change, nor in the tube containing boiled enzyme. 

 Trypsin thus acts only in faintly alkaline solution of O'2-o*5 per cent, 

 concentration. 



As substrate polypeptides, such as glycyl-tyrosine, glycyl-tryptophan and a 

 peptone from silk have been used to detect trypsin. The tyrosine separates 

 out and the bromine water reaction for tryptophan becomes positive. 



