ENZYMES AND THEIR ACTION. 13 



It has been determined that disaccharide solutions will not 

 reduce Barfoed's reagent until after they have been heated for 9-10 

 minutes on a boiling water-bath in contact with the reagent. 1 

 Therefore in the above test, if the tube containing the unboiled 

 extract exhibits any reduction after being heated as indicated, for 

 a period of five minutes or less, and the control tube containing 

 boiled extract shows no reduction, it may be concluded that lactase 

 was present in the intestinal extract. 2 



7. Preparation of an Extract of Maltase. 3 Treat the finely 

 divided epithelium of the small intestine of a cat, kitten, or pig 

 (embryo or adult) with about three volumes of a two per cent solu- 

 tion of sodium fluoride and permit the mixture to stand at room 

 temperature for twenty-four hours. Strain the extract through 

 cloth and use the strained material in the following demonstration. 



8. Demonstration of Maltase. Proceed exactly as indicated in 

 the demonstration of lactase, above, except that a one per cent solu- 

 tion of maltose is substituted for the lactose solution. The extract 

 used may be prepared from the upper part of the intestine of a cat, 

 kitten, or pig (embryo or adult). In the case of lactase, as indi- 

 cated, the intestine used should be that of a kitten, puppy, or pig 

 (embryo). 



V. EREPSIN. 4 



1. Preparation of Erepsin. Grind the mucous membrane of 

 the small intestine of a cat, dog or pig, with sand in a mortar. 

 Treat the mortared membrane with toluene- or chloroform-water 

 and permit the mixture to stand, with occasional shaking, for 24-72 

 hours. 5 Filter the extract thus prepared through cotton and use 

 the filtrate in the following experiment. 



2. Demonstration of Erepsin. To about 5 c.c. of a one 

 per cent solution of Witte's peptone in a test-tube add about one 

 c.c. of the erepsin extract prepared as described above and make 

 the mixture slightly alkaline (o.i per cent) with sodium carbonate. 

 Prepare a second tube containing a like amount of peptone solu- 

 tion but boil the erepsin extract before introducing it. Place the 



x The heating for 9-10 minutes is sufficient to transform the disaccharide into 

 monosaccharide. 



2 The reduction would, of course, be due to the action of the dextrose and 

 galactose which had been formed from the lactose through the action of the 

 enzyme lactase. 



3 For a discussion of this enzyme see p. 55. 



4 Also called erepsase. For a discussion of this enzyme see p. 143. 



5 The enzyme may also be extracted by means of glycerol or alkaline " physi- 

 ological" salt solution if desired. 



