ENDOTRYPTASE. 555 



probable derivatives of pyridin observed by SCHROTTER (I.) in 

 the fusel oil (see p. 505) of a molasses distillery. These discoveries 

 cannot be attributed with certainty to the activity of the yeast. 

 Other micro-organisms may have been concerned to some extent, 

 and the products in question may have partly originated through 

 the action of boiling heat on the residual proteids in the fermented 

 liquids. The small amount of ammonia found to result from the 

 pure autodigestion of yeast renders it at least improbable that any 

 considerable production of volatile amine bases occurs, since most 

 of these readily furnish ammonia. These fission products, how- 

 ever, really facilitate the more intimate chracterisation of the 

 proteolytic enzyme of yeast. As pointed out by Kutscher and 

 Lohmann, they correspond exactly with those found by these 

 authors in trypsin digestion. Salkowski, as well as Geret and 

 Hahn, had already classed the enzyme as a tryptic enzyme, and 

 regarded the identification of the raonamino acids as sufficient for 

 this characterisation. However, in spite of the identity of the 

 fission products, it would not be advisable to assume that yeast 

 endotryptase is the same as pancreatic tryptase, since two essential 

 points of difference exist between them. Tn the first place, the 

 action of yeast endotryptase is greatly facilitated by an acid 

 reaction, and retarded by an alkaline reaction, in which respect 

 its behaviour is the antithesis of that of pancreas tryptase ; and, 

 secondly, the autodigestion of expressed yeast juice yields sub- 

 stances that do not furnish the biuret reaction more than transi- 

 torily, if at all, the reaction quickly disappearing even when 

 peptone and albumoses are added. Nevertheless, despite these 

 differences, it must be maintained that we have here to deal with 

 an enzyme belonging to the group of tryptases, more particularly 

 because of the fission products obtained. For whether, as assumed 

 by LAWROW (I.), such an extensive decomposition of the protein 

 molecule can also be effected by peptases (the influence of which 

 is favoured by an acid reaction) must still be considered doubtful, 

 since in Lawrow's experiments with sliced pigs' stomachs it was 

 impossible to preclude the occurrence of autolytic processes 

 inseparable from the actual pepsin action. 



The practically and theoretically important question of the 

 conditions under which yeast endotryptase is formed and exerts 

 its action is less easily answered. WILL (XXXV.), who examined 

 a large number of pure cultures of various species of yeast in 

 wort-gelatin, and observed liquefaction (commencing in the path 

 of the stab) within 18-20 days at 20 0., ascertained that the 

 more rapidly liquefying species (Mt/coderma and Willia) are in 

 general more exacting as regards the supply of oxygen. When 

 the inoculating material was mixed with the warmed (and thereby 

 liquefied) gelatin, proteolysis was found to commence in 7-55 

 days, the time being proportional to the requirements of the 

 species in respect of oxygen. On the basis of these and other 



