PRODUCTION OF ENZYMES 111 



All chemical reactions have such temperature limits, the 

 distinction is that for enzymes as for living substance the 

 range is relatively narrow. 



(6) High temperatures destroy enzymes. All in water 

 are destroyed by boiling in time and most at temperatures 

 considerably below the boiling-point. When dry, many will 

 withstand a higher degree of heat than 100° before they are 

 destroyed. 



(c) Temperatures below the minimum stop their action, 

 though they are not destroyed by cold. ' 



{d) Many poisons and chemical disinfectants (Chapter 

 XIV) which kill living organisms will also stop the action of 

 enzymes, though generally more of the substance is required, 

 so that it is possible to destroy the living cells by such means 

 and yet the action of the enzyme will continue. 



(e) Most enzymes have an optimum reaction of medium 

 either acid, alkaline or neutral, depending on the particular 

 enzyme, though some few seem to act equally well in a 

 considerable range on either side of the neutral point. 



The final test for an enzyme is the chemical change it brings 

 about in the specific substance acted on. 



The most prominent characteristic of enzymes is that 

 they bring about very great chemical changes without them- 

 selves being appreciably affected. This property is also 

 shown by many inorganic substances which are spoken of 

 as "catalytic agents" or "catalyzers" so that enzymes are 

 sometimes called "organic catalyzers." The function of 

 catalytic agents seems to be to hasten the rate of a reaction 

 which would occur spontaneously, though in a great many 

 cases with, extreme slowness. 



Just how enzymes act is not certain and probably will not 

 be until their composition and constitution are known. 

 Most probably they form a combination with the substance 

 acted on (the substrate) as a result of which there is a rear- 

 rangement of the atoms in such a way that new compounds 

 are formed, nearly always at least two, and the enzyme is 

 at the same time set free. It is rather remarkable that 

 chiefly optically active substances are split up by en- 

 zymes and where two modifications exist it is usually the 



