AGRICULTURAL CHEMISTRY^ — AGROTECHNY, 703 



shown in the digestion of raw and coaguhited egg white, fibi-in, edestin, and 

 excelsin, whether one take as the gage of digestion the appearance of tryptophan, 

 leucin and tyrosin, the conversion into products not precipitated by hot trichlo- 

 racetic acid or the rate of sohition of insoluble protein. HON also accelerates 

 the clotting of milk and the liquefaction of gelatin. The bearing of this ou the 

 evidence for the existence of more than one proteolytic enzym in papain is 

 discussed. 



" Of various substances tried, hydrogen sulphid was the only one which pro- 

 duced an acceleration of digestion by papain comparable to that effected by PICN. 



"The activity of HCN can not be attributed (a) to a peculiarly favorable 

 concentration of hydrogen ions; (b) to the destruction of an inhibiting substance 

 in the papain; (c) to the destruction of an inhibiting substance in the sub- 

 stratum; (d) to a permanent denaturation of the substratum; or (e) to the 

 activation of a papain zymogen. Pending further investigation, nothing remains 

 but to compare the behavior of HCN with that of the so-called co-enzyms. 



" The rapid digestion of egg-white which papain effects when mixtures of the 

 enzym and protein are heated to boiling has been confirmed ; and it has been 

 shown that typical plant proteins — excelsin and edestin — are digested with simi- 

 lar rapidity at 80°. Under tlie especially favorable conditions established by 

 the presence of HCN, digestion at 80° proceeds to the amino-acid stage. 



" In regard to the marked deterioration which papain is said to undergo when 

 ir stands with uncoagulated egg-white, it appears that this can not be considered 

 a constant characteristic of the enzym in question, inasmuch as it was found 

 that in the 6 samples of papain which were studied the spontaneous deteriora- 

 tion of the enzym on standing in solution in every case more than accounted for 

 the loss of activity when it stood with the protein. Egg white, if anything, 

 protects papain from deterioration. 



" The fresh latex of the iiawpaw resembles the dried material in its behavior 

 toward antiseptics and temperature, and in the phenomena of deterioration. 



"Extracts of Ascaris which are strongly antiseptic and antitryptic exert no 

 inhibition over papain pi'oteolysis. The behavior of papain toward Ascaris 

 antieiizyms, the acceleration phenomena induced by HCN, and the peculiar tem- 

 perature relations, place papain in a different category from pepsin, trypsin, and 

 animal erepsin. Data already recorded or available from other plants in respect 

 to the HCN acceleration and other features place papain in contrast with other 

 vegetable enzyms. The facts reported do not exclude the possibility of the 

 sinndtaneous presence of more than one enzym in the pawpaw latex." 



The study of enzyms by means of the synthetical polypeptids, A. H. 

 KoELKER {Jour. Biol. Cheni., 8 (1910), No. 2, pp. lJi5-115). — "For the study of 

 the proteolytic enzyms, racemic alanyl-glycin can be applied with great ac- 

 curacy, using the optical method. Solutions of d-alanyl-d-alaniu and of racemic 

 alanyl-glycin remain unchanged when they are allowed to stand at 15 to 20° 

 for a period of 13 months, if toluol has been used as preservative. This proves 

 that within the time mentioned neither water nor bacteria have any influence 

 in hydrolyzing the dlpeptids. Buchner's grinding and pressing method yields 

 the most active enzym. The precipitation with alcohol can not be used to 

 advantage in the purification of the active principle. The active principle 

 which hydrolyses alanyl-glycin has the property of dialyzing through parch- 

 ment. The solution of the enzym which has been freed from most of the solids 

 by dialysis can be evaporated to dryness and redissolved without being im- 

 paired in its activity. The ferment is still i)resent after 1.3 days" digestion at 

 37°. Heating the solution of the enzym to a tenii)erature of 7.'")° for (5 minutes 

 destroys the active principle completely. Sodium chlorid has no inlluence ujum 

 the rate of hydrolysis. It has, however, the property of preserving the enzym 



