ADAPTIVE AND CONSTITUTIVE ENZYMES 



93 



(except for the maltose enzyme which also appeared in 

 the absence of any carbohydrate). That the galactose 

 enzyme appeared when L. nies enter oides was grown on 

 lactose is not surprising since lactose is built up of glucose 

 and galactose units. 



Usually the glucose splitting enzymes are constitutive, 

 but an exception is found in the case of the pentose 

 fermenting organism, Lactobacillus pentoaceticus , in which 

 the glucose enzyme is adaptive and the xylose and 

 arabinose enzj^mes constitutive, as may be seen from 

 Table 7 (also due to Karstrom) : — - 



Table 7 



An example of the second type of constitutive enzyme, 

 those showing increased production in presence of the 

 substrate, is given by the formation of the sucrose 

 splitting enzyme by Esch. coli in considerably greater 

 amount when the organism is grown on sucrose then 

 when it is grown on media containing glucose, maltose 

 or lactose, all of w^hich give rise to the production of some 

 sucrase, however. 



Quastel has studied the production of the enzymes 

 catalase, urease andfumarase by the organism Micrococcus 

 lysodeikticus in different media. This organism was 

 chosen because it possesses the peculiar property of being 

 very easily lysed by egg-white with consequent liberation 

 of its endo-enzjrmes into the medium. After liberation 



