CHAPTER XII 

 INFLUENCE OF OTHER FACTORS UPON ENZYMES AND CELLS 



TEMPERATURE PHYSICAL AND CHEMICAL AGENTS NEGATIVE 

 CATALYSTS, ANTI-CATALYSTS, ANTI-FERMENTS, AND ANTI- 

 ENZYMES ZYMO-EXCITATORS OR KINASES AUTO-CATALYSIS 

 AND INFECTION SPECIFIC NATURE OF CATALYTIC ACTION 

 THE CHEMICAL AND PHYSICAL NATURE OF ENZYMES THE SO- 

 CALLED INORGANIC ENZYMES OR METAL-SOLS. 



IT is characteristic of all enzymes that they are very sensitive to 

 changes of temperature both as regards their stability and as 

 regards their rapidity of action. 



The stability of the different enzymes varies very widely, but 

 as a general rule it may be stated that the rate of destruction 

 rapidly increases with the temperature, although this may lie much 

 below that at which they are most rapidly destroyed. The amount 

 of enzyme destroyed also varies with the substances present in 

 solution; thus the products of reaction in all cases exercise a pro- 

 tective action against rise in temperature which has been ascribed 

 to the formation of a compound between the enzyme and the 

 products of its activity. 



All enzymes in aqueous solution are rapidly destroyed at about 

 the coagulation temperature of proteids (65 to 75 C.) and a 

 coagulum usually appears in the solution. 



Even at body temperature and below it many are, however, 

 rapidly destroyed, especially in the absence of a protective sub- 

 stratum. Thus Vernon has shown that trypsin in nearly pure 

 solution is rapidly destroyed at 38 C., but is protected from such 

 rapid destruction by the presence of protein. The subject has 

 been further investigated by Bayliss, who finds that trypsin in 

 solution slowly loses activity even at C. 



The action of heat upon enzymes in organic solvents is much 

 less marked than in aqueous solutions ; thus Pavy found that 

 the diastatic ferments of the liver and pancreas are not destroyed 



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