CHAPTER III 



BACTERIAL ENZYMES 



Enzyme action 



The chemical activities of bacteria and other living tissues 

 are due to the catalytic action of enzymes. Enzymes are 

 organic substances which are produced by living cells and 

 which act as catalysts of specific reactions. They have 

 properties similar to those of catalysts used in chemical 

 processes in that they speed up the velocity of a reaction 

 without altering the nature or proportions of the products 

 and without adding any energy to the reacting system. 

 Other things being equal, the velocity of the reaction is 

 proportional to the concentration of the catalyst or enzyme. 

 Enzymatic activity is dependent upon certain physical con- 

 ditions being suitable; thus an enzyme is active over a small 

 range of pH only, the value at which it displays maximal 

 activity being known as the " optimal joH." For the 

 majority of enzymes this optimal ^H value lies between 

 pH 5 and 8, but in individual cases it may be within wider 

 limits of 2-10. A catalyst can speed up a reaction which is 

 already proceeding slowly, but it cannot by itself initiate a 

 reaction, and it is as yet uncertain whether this is or is not the 

 case with enzymes. Many reactions which take place in the 

 presence of living tissues will not noticeably take place in their 

 absence, but, as has already been pointed out, many chemical 

 reactions occur at too slow a rate to be perceived by man 

 through his senses. It is not illogical therefore to regard 

 enzymes as catalysing reactions which are normally occurring 

 at an insensible rate, but many authorities are of the opinion 

 that enzymes, by straining the structure of the molecule upon 

 which they act and so rendering it more susceptible to change, 

 can initiate new reactions. Enzymes also differ from most 



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