376 ENZYMES 



TRYPTOPHANE REACTION. 



The presence of tryptophane is an indication of the activity 

 of trypsin-like proteolytic ferments. Tryptophane may occur 

 naturally in the sap of the plant, its presence being associated 

 with the ripening of fruits and the germination of protein-con- 

 taining seeds.* 



In order to ascertain whether the enzyme be a tryptic one, 

 a solution of it, or some of the more or less crude plant-extract, 

 is added to a solution of peptone and placed in an incubator 

 for some time, according to the strength of the solutions, kept 

 at a temperature of 40. A little toluol may be added as an 

 antiseptic. To test, a few drops of the liquid are placed in a 

 watch glass, acidified with acetic acid, and then a little chlorine 

 water is added. The appearance of a marked yellow to pink 

 coloration indicates the presence of tryptophane. If performed 

 on a large scale, the liquid may be finally shaken up with 

 amyl alcohol which dissolves the pink chlorine compound and 

 eventually rises to the top. It may be separated by means 

 of a small separating funnel and spectroscopically examined. 

 An absorption band will be observed on the yellow side of 

 the thallium line (571 - 540^/4). 



Another test for tryptophane consists in mixing the 

 suspected solution with a little glyoxylic acid and carefully 

 adding concentrated sulphuric acid so that the latter forms a 

 separate layer at the bottom of the test tube. After a short 

 time a purple ring is produced at the junction of the two 

 liquids, and on careful agitation the colour extends over the 

 whole solution. If pepsin be used in the above experiments, 

 it must be well washed in water and alcohol before use. 



QUANTITATIVE DETERMINATION OF THE ACTIVITY OF 

 PROTEASES. 



Schultz f followed the course of the action of pepsin on 

 egg albumen by precipitating out the albumen from time to 

 time and examining the optical activity of the peptone solution. 



Sjoqvist,j on the other hand, measured the electrical con- 



* Vines: "Ann. Bot.," 1902, 16, i ; 1903, 17, 237, 597. 

 f Schultz : " Zeit. phys. Chem.," 1885, 9, 577. 

 JSjoqvist: " Skand. Arch. f. Physiol.," 1895, 5, 317. 



