98 



ENZYMES 



instance, contains protein which is not digested by gastric protease 

 as long as the blood supply is intact. Occlusion of the blood 

 supply to any part leads to the formation of a gastric ulcer. 

 Parasitic worms live in contact with enzymes that would cause 

 rapid digestion in the event of their death. Neither Cohnheim 

 nor Bayliss is inclined to accept the anti-enzyme idea as correct. 

 (1) The latter has shown that the phenomenon can be explained 

 without any such hypothesis e.g. by the adsorption of the enzyme 

 by another colloid. Agitation of a suspension of trypsin with 

 charcoal results in a loss of digestive activity due to the adsorption 

 of the enzyme by the charcoal. The charcoal here acts as an 

 anti-enzyme. (2) Enzymes as colloids are sensitive to any altera- 

 tion in their environment. A slight alteration in salt content, 

 colloid or water concentration, or P H leads to alteration in their 

 power of adsorbing or being adsorbed by their substrate. 



Specificity. 



Each enzyme acts on a specific substrate, and if the substrate 

 is a mixture of optical isomers, one of these (and always the same 

 one) will be selected for preferential treatment. Examples may 

 make this clearer. If maltase be added under suitable conditions 

 to the following disaccharides it will be found to act on one only 

 maltose. 



TABLE XVI. 



