V] HYDROLYZINO ENZYMES 75 



Thi.s simple method may also be adopted for showing the diastatic activity of 

 leaves. Instead of germinating barley, a few IcaHcts of the Pea {Pimm satiouvi) or 

 Clover {Tnfolium pratense) should be pounded uj) in a mortar and extracted with 

 50 CO. of water and tiltered. 



Expt. 79. To shoio that leaf-diastase is still active after drying the leaves at 

 temperatures not higher than 38° C. Take 10 gms. of fresh Pea leaves and dry by 

 spreading them in the sun. Then powder and finally dry in an incubator at 38' C. 

 Make up 500 c.c. of a 1 % solution of starch (see Expt. 55). To this add the dry leaf 

 powder together with a few drops of toluol and keep in an incubator at 38" C. Test 

 the solution with iodine from time to time and note the hydrolysis of the starch. 



Expt. 80. To show that the action of diastase is impaired hy contact of the enzyme 

 with alcohol. Pound up 10 gms. of fresh Pea leaves, add 100 c.c. of water, a few drops 

 of toluol and allow the mixture to stand for 12 hrs. Filter off the extract, and 

 add at least an equal bulk of 96-98 % alcohol. A white precipitate is produced 

 which, among other substances, contains crude diastase. Filter, and wash the 

 precipitate with a little water into 500 c.c. of a 1 "/o starch solution. Add a few drops 

 of toluol, plug with cotton-wool and put in an incubator. Test with iodine from 

 time to time. It will be found that the hydrolysis takes place much more slowly 

 than in the previous experiments. 



E.xpt. 81. To show that the action of diastase is inhibited hy tannic acid. Take 

 about 0-5-1 gm. of dried powdered Pea leaf. Let it .stand for about 12 hrs. in 50 c.c. 

 of water containing a few drops of toluol. Filter off, and to equal amounts of the 

 filtrate in two small flasks add about 10 c.c. of a 1 *'/o starch solution. Add also 

 10 c.c. of a 0-5 % tannic acid solution to one test-tube. Put both tubes into an 

 incubator. Test with iodine solution after a few hours. It will be found that the 

 tannic acid has inhibited the action of the diastase. 



Maltase. This enzyme hydrolyzes maltose into two molecules of 

 glucose : 



C1.H22O11 + H.,0 = 2CoHi.,0,i- 



Investigations upon maltase have, until recently, produced rather 

 contradictory results, but later work (Davis, 12: Daish, 18, 14) has led to 

 more satisfactory conclusions. The latter show that maltase is most 

 probably present in all plants in which hydrolysis of starch occurs. It 

 has been detected in leaves of the Nasturtium (Tropaeolum), the Potato 

 (Solanum), the Dahlia, the Turnip {Brassica), the Sunflower {Helianthus) 

 and the Mangold {Beta), and it is most probably widely distributed in 

 foliage leaves. Its detection is not easy for various reasons which are 

 as follows. It is not readily extracted from the tissues by water: it is 

 unstable, being easily destroyed by alcohol and chloroform. Its activity 

 is also limited or even destroyed at temperatures above 50° C Hence 

 the extraction of maltase, by merely pounding up tissues with water, 

 does not yield good results : moreover, as an antiseptic, toluol must be 



