ENZYMES AND THEIR ACTION. I I 



4. Demonstration of Vegetable Lipase. The lipolytic action 

 of the lipase prepared from the castor bean, as just described, may 

 be demonstrated in a manner entirely analogous to that used in the 

 Demonstration of Pancreatic Lipase, see p. 10. Proceed as indi- 

 cated in that experiment and substitute the vegetable lipase powder 

 for the neutral extract of pancreatic lipase. The type of action is 

 entirely analogous in the two instances. 



An experiment similar to Experiment 2, p. 149, may also be tried 

 if desired. In this experiment 0.2 c.c. of either ethyl butyrate or 

 ainyl acetate may be employed. 



IV. INVERTASES. 1 



1. Preparation of an Extract of Sucrase. 2 Treat the finely 

 divided epithelium of the small intestine of a dog, pig, rat, rabbit, or 

 hen, with about three volumes of a two per cent solution of sodium 

 fluoride and permit the mixture to stand at room temperature for 

 twenty-four hours. Strain the extract through cloth or absorbent 

 cotton and use the strained material in the following demonstra- 

 tion. 



2. Demonstration of Sucrase. To about 5 c.c. of a one per 

 cent solution of sucrose, in a test-tube, add about one cubic centi- 

 meter of a two per cent sodium fluoride intestinal extract, prepared 

 as described above. Prepare a control tube in which the intestinal 

 extract is boiled before being added to the sugar solution. Place 

 the two tubes at 38 C. for two hours. 3 Heat the mixture to boil- 

 ing to coagulate the protein material; filter, and test the filtrate by 

 Fehling's test (see p. 27). The tube containing the boiled extract 

 should give no response to Fehling's test whereas the tube con- 

 taining the unboiled extract should reduce the Fehling's solution. 

 This reduction is due to the formation of invert sugar (see p. 41") 

 from the sucrose through the action of the enzyme sucrose which 

 is present in the intestinal epithelium. 



3. Preparation of Vegetable Sucrase. Thoroughly grind 

 about 100 grams of brewer's yeast in a mortar with sand. Spread 

 the ground yeast in thin layers on glass or porous plates and dry 

 it rapidly in a current of dry, warm air. Powder this dry yeast, 

 extract it with distilled water and filter. Pour the filtrate into 



1 The inverting enzymes of the alimentary tract; Mendel and Mitchell : 

 American Journal of Physiology, 1907-08, XX, p. 81. 



~ For a discussion of this enzyme see p. 144. 



3 If a positive result is not obtained in this time permit the digestion to 

 proceed for a longer period. 



