ENZYMES AND THEIR ACTION. 9 



3. Preparation of Vegetable Amylase. Extract finely ground 

 malt with water, filter and subject the filtrate to alcoholic fermenta- 

 tion by means of yeast. When fermentation is complete filter off 

 the yeast and precipitate the amylase from the filtrate by the addi- 

 tion of alcohol. The precipitate may be filtered off and obtained in 

 the form of a fine white powder. 



4. Demonstration of Vegetable Amylase. This enzyme may 

 be demonstrated according to the directions given under Demonstra- 

 tion of Salivary Amylase, p. 8, with the exception that the saliva 

 used in that experiment is replaced by an aqueous solution of the 

 vegetable amylase powder prepared as described above. 1 



II. PROTEASES. 



1. Preparation of Gastric Protease. 2 Treat the finely com- 

 minuted mucosa of a pig's stomach with 0.4 per cent hydrochloric 

 acid and extract at 38 C. for 24-48 hours. The filtrate from 

 this mixture constitutes a very satisfactory acid extract of gastric 

 protease (see p. 122). 



2. Demonstration of Gastric Protease. Introduce some pro- 

 tein material (fibrin, coagulated egg-white, or washed lean beef) 

 into the acid extract of gastric protease prepared as above described, 3 

 add an equal volume of 0.4 per cent hydrochloric acid and place the 

 mixture at 38 C. for 2-3 days. Identify the products of digestion 

 according to directions given on p. 122. 



3. Preparation of Pancreatic Protease. 4 A satisfactory ex- 

 tract of this enzyme may be made from the pancreas of a pig or 

 sheep according to the directions given on p. 144. 



4. Demonstration of Pancreatic Protease. Into an alkaline 

 extract of pancreatic protease, 5 prepared as directed on p. 144, in- 

 troduce some fibrin, coagulated egg-white or lean beef and place 

 the mixture at 38 C. for 2-5 days. 6 At the end of that period 



1 If desired the first aqueous extract of the original malt may be used in this 

 demonstration. Commercial taka-diastase may also be employed. 



2 Also called pepsin, pepsase, gastric proteinase, and acid protease. For a dis- 

 cussion of this enzyme see p. 120. 



3 If so desired a solution of commercial pepsin powder in 0.2 per cent hydro- 

 chloric acid may be substituted. 



4 Also called trypsin, trypsase, pancreatic proteinase and alkali proteinase. 

 For a discussion of this enzyme see p. 141. 



5 A 0.25 per cent sodium carbonate solution of commercial trypsin may be 

 substituted. 



8 A few c.c. of toluene or an alcoholic solution of thymol should be added to 

 prevent putrefaction. 



