402 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



III. Emulsin. 



Emulsin is prepared most easily from almonds. The almonds are ground 

 and the oil is pressed out. The residual cake is treated with water at room 

 temperature. The filtered solution is acidified with acetic acid (2 drops per 

 100 c.c.) to precipitate proteins. The filtrate is treated with an equal volume 

 of alcohol. The enzyme preparation is thrown down, washed with alcohol 

 and ether and dried. The precipitate can be immediately redissolved in water 

 and used in experiments with emulsin. 



A substrate of 2 per cent salicin is conveniently used. 5 c.c. of 

 salicin solution are placed in each of two test tubes. To the one are 

 added 5 c.c. of emulsin solution ; to the other are added 5 c.c. of boiled 

 emulsin solution. The two tubes are placed in a water-bath at 40 

 for 1 5-30 minutes or longer ; in the latter case I per cent, of 

 toluene should also be added. The solutions are tested with Fehling's 

 solution. Reduction occurs in the first tube in which the salicin has 

 been hydrolysed to saligenin and glucose. 



Amygdalin may also be used as substrate and the formation of 

 hydrogen cyanide tested for with picric acid paper. 1 This method has 

 been used by Armstrong for detecting emulsin in plants. The plant 

 leaf, etc., is put into a small test tube containing a drop of chloroform, 

 and a few drops of amygdalin solution ; the test tube is closed with a 

 cork, to which is attached a piece of picric acid paper. If emulsin be 

 present, the paper becomes brick-red in colour from the action of 

 hydrogen cyanide. In a similar way the presence of amygdalin, of 

 emulsin together with amygdalin, may be tested for. 



IV. Lactase and Maltase. 



Since both lactose and maltose reduce Fehling's solution their 

 hydrolysis by enzymes is difficult to demonstrate. It can only be 

 satisfactorily demonstrated by the measurement of the reducing 

 power. Lactose and maltose do not reduce Barfoed's reagent which 

 is reduced by glucose and monosaccharides. Hence this reagent will 

 serve to show the presence of these enzymes thus : 



Demonstration of Lactase in Intestinal Mucous Membrane. 



The mucous membrane is scraped off, ground up with sand to break 

 the cells and kept in water with I per cent of toluene for 12-24 hours. 

 The solution is strained through muslin and divided into two nearly 

 equal parts, say of 1 05 and 1 1 o c. c. The larger part is boiled and cooled. 



100 C.G of unboiled solution are added to 100 c.c. of 5 per cent 

 lactose solution in a small flask (l). loo c.c. of boiled solution are 

 added to 100 c.c. of 5 per cent, lactose solution in a small flask (2). 

 I cc of toluene is added to each ; the two flasks are corked and 

 kept at 37 for 1-4 days. 



Flask (i) will show a reduction when tested with Barfoed's reagent 



Flask (2) will not show a reduction ; if there is a slight reduction, 

 this will be due to the presence of glucose in the extract. 



1 Filter paper moistened with a solution of i gm. picric acid + 10 gm. of Na 2 CO 8 in 

 100 c.c. of water. 



