HYDROLYTIC ENZYMES 79 



4. Enzymes are usually characterized by great sensitiveness to 

 comparatively low temperatures and to many poisons. This prop- 

 erty formerly was used to determine whether or not a reaction was 

 being catalyzed by an enzyme; but there are known a few cases in 

 which the enzyme is not destroyed by boiling water. The great 

 majority of all enzymes are, however, destroyed by a temperature 

 somewhat below 100 C ., many even as low as 60 C . This property 

 is no doubt due to the colloidal nature of the ferment which, on 

 being heated, coagulates probably much as does a protein, for it 

 is well known that enzymes are more sensitive in the presence of 

 water than in its absence. 



Although the addition of hydrocyanic acid or formaldehyde to 

 a media in which reactions are being catalyzed by enzymes puts 

 a stop to the reaction, yet the concentration necessary is usually 

 greater than that which can be borne by the living protoplasm. 

 This makes it possible to kill the cell and still have the enzyme 

 reactions going on in the medium by carefully adjusting the con- 

 centration of the antiseptic used. 



Various methods are used in the extraction of enzymes. Some 

 readily diffuse out of the cell and may be taken up with water; 

 others are extracted with glycerin or acids; in still other cases it 

 is necessary to decompose completely the cells as did Biichner 

 in obtaining zymase. The resulting product is then often purified 

 by alcoholic or other precipitants. This drastic treatment, how- 

 ever, often impairs the activity of the ferment. 



Classification. Fuhrmann has classified enzymes of bacterial 

 origin into four types as follows: 



A. Schizases (hydrolytic) cleavage enzymes: 



1. Carbohydrate-splitting enzymes. 



2. Glucoside-splitting enzymes (synaptase). 



3. Fat-splitting enzymes. Lipases (esterases). 



4. Proteases, protein-splitting enzymes, pepsin, trypsin 



(lysins, coagulases). 



B. Fermentation enzymes: 



Zymase urease, lactic-acid enzyme. 



C. Oxidizing enzymes : 



Tyrosinase, acetic bacteria, oxidase. 



D. Reducing enzymes: 



Reductase. 



Hydrolytic Enzymes. As a type of the hydrolytic enzymes which 

 act upon carbohydrates, we may take maltase which converts 

 maltose into dextrose according to the following equation: 



+ H 2 O C 6 Hi2O 6 + 



Maltose. Dextrose. Dextrose. 



Maltase is an enzyme which occurs in yeast, many bacteria, and 

 numerous other cells. It is of special interest inasmuch as it is 



