ENZYMES OF PROTEIN SUBSTANCES 59 



ENZYMES OF PROTEIN SUBSTANCES 

 Proteases 



Geret and Hahn have shown that yeast juice dissolves the floccu- 

 lent coagulum of albuminous materials like fibrin or coagulated albumin. 

 The juice contains a proteolytic enzyme or endotryptase, which is ca- 

 pable of being isolated in comparatively pure state. This enzyme plays 

 a very important role in the life of the cell. The investigations of Gro- 

 mow and Gregoriew 1 have shown that this endotryptase exercises a 

 powerful action on the juice itself and that it alters and digests it rapidly 

 at 30-35. This action explains the rapidity with which zymase is 

 destroyed. This enzyme is more active in an acid than in an alkaline 

 medium, being favored by 0.2 per cent of hydrochloric acid. It seems 

 to approach trypsin more closely in characteristics than pepsin, for 

 Geret and Hahn have obtained a fairly complete degradation of albu- 

 minoid substance as with trypsin. The presence of leucine and tyrosine 

 has been shown. 



Endotryptase liquefies gelatin according to Hahn 2 and Hjort. This 

 is an intracellular enzyme and not able to pass through the cell mem- 

 brane. This fact makes it difficult to understand how the yeast is able 

 to liquefy gelatin. It is common knowledge that the yeasts liquefy and 

 peptonize, as has been shown by the works of Linder, Boullinger, Bei- 

 jerinck and Astari. Also one is obliged to admit with Will that endo- 

 tryptase, normally, intracellular, is able under certain conditions to 

 diffuse through a membrane. This diffusion occurs at various phases 

 of its development, and especially in cells which are not in normal con- 

 dition (dead or diseased cells). 



We have stated that, according to Boullinger, certain yeasts se- 

 crete a casease. The formation of a curd in milk after a few months 

 was determined. This coagulum dissolves little by little and the liquid 

 becomes yellowish. The transformation of the casein, yields tyrosine, 

 leucine and other ammoniacal bodies. Bochicchio has verified the 

 secretion of rennin by Lactomyces inflans caseigrana. Rapp has ob- 

 served the presence of casease in certain yeasts. Dombrowski has 

 shown that many of the yeasts peptonize milk strongly, especially 

 S. lactis v. 



According to Boullinger, there is a relation between the yeasts 



1 Gromow, T., and Gregoriew, O. Die Arbeit der Zymase und der Endo- 

 tryptase in den abgetoteten Hefezellen unter verschiedenen Verhaltnissen. Zeit. 

 f. physiol. Chemie, 2, 1904. 



2 Hahn, M., and Geret, Z. Ueber das Hefe Endotryptase, Zeit. Biol. 22, 

 1900. 



