PRODUCTION OF ENZYMES 111 



ucts of complex protein decomposition, such as proteoses, 

 peptones and amino-acids. A variety of the ''sphtting 

 enzymes" is the group of — 



" Coagulases/' or coagulating enzymes, as the rennet (lab, 

 chymosin) which curdles milk and fibrin ferment (thrombin, 

 thrombase) which causes the coagulation of blood. These 

 apparently act by splitting up a substance in the fluids 

 mentioned, after which splitting one of the new products 

 formed combines with other compounds present (usually a 

 mineral salt, and in the cases mentioned a calcium salt) to 

 form an insoluble compound, the curd or coagulum. 



Another variety is the "activating" enzymes or ''kinases/^ 

 such as the enterokinase of the intestine. The action here 

 is a splitting of the zymogen or mother substance or form in 

 which the enzyme is built up by the cell so as to liberate the 

 active enzyme. 



Of a character quite distinct from the splitting enzymes 

 are: 



II. The zymases. Their action seems to be to cause a 

 "shifting on rearrangement of the carbon atoms" so that new 

 compounds are formed which are not assumed to have 

 been constituents of the original molecule. Most commonly 

 there is a closer combination of the carbon and oxygen 

 atoms, frequently even the formation of CO2, so that con- 

 siderable energy is thus liberated. Examples are the zymase 

 or alcoholase of yeast, which converts sugar into alcohol and 

 carbon dioxide: C6H12O6 = 2C2H6O + 2CO2; also urease, 

 which causes the change of urea into ammonia and carbon 

 dioxide. Another common zymase is the lactacidase in 

 lactic acid fermentation. 



III. Oxidizing enzymes also play an important part in 

 many of the activities of higher plants and animals. Among 

 the bacteria this action is illustrated by the formation of 

 nitrites, nitrates and sulphates and the oxidation of alcohol 

 to acetic acid, as already described. 



IV. Reducing enzymes occur in many of the dentrifying 

 bacteria and in those which liberate H2S from sulphates. 

 A very widely distributed reducing enzyme is "catalase," 

 which decomposes hydrogen peroxide. 



