CHAPTER XIX 

 ENZYMES OF BACTERIA 



SELMAN A. WAKSMAN 



New Jersey Agricultural Experiment Station, New Brunswick, N.J. 



DEFINITION AND PROPERTIES OF ENZYMES 



Pasteur was the first to establish the difference between "formed" or "organized" 

 ferments, which bring about various reactions, such as alcoholic and acid fermenta- 

 tions, through the action of the living cell, and "unorganized ferments," such as 

 diastase, pepsin, etc., later designated by Kiihne as "enzymes," which are active in the 

 absence of living cells. A distinct difference was thus made between "metabolic" 

 processes and "enzymatic" processes, or between a ferment as an organized living 

 cell and an enzyme as a product of the cell, active inside or outside of the cell. How- 

 ever, further studies, especially the contributions of Buchner on the intracellular 

 enzymes bringing about alcoholic and acid fermentations, finally established the fact 

 that no essential difference exists between enzymes and ferments. 



An enzyme is a catalytically active substance which is produced by living cells 

 and the action of which is independent of the life-processes of the cell. Enzymes are 

 capable of accelerating the rate of chemical reactions and remain themselves un- 

 changed. Seemingly the enzyme does not enter into the reaction itself. In certain 

 cases enzymes may accelerate the reaction in one direction more than in another, as 

 in the following illustration: 



2H.O-f0.^2H.O. 



when only the reaction from right to left is accelerated by catalase. 



Enzymes act specifically, i.e., they act upon substances of definite structural and 

 stereoisomeric configuration. This specificity of enzymes is independent of the degree 

 of their purity. However, it has not been demonstrated as yet that enzymes are 

 definite chemical substances; no enzyme has been isolated in a pure state. Enzymes 

 must be defined upon the basis of their action rather than their chemical nature. 



Enzymes possess certain physical properties, such as being apparently amphoteric 

 electrolytes and colloids, enabling them to form absorptive compounds; they also 

 possess definite structures which give them a specific affinity to the substrates upon 

 which they act. 



NATURE OF ENZYMES 



The nature of the structure of enzymes is still imperfectly understood, especially 

 for a number of enzymes not yet separated from the cell constituents, notably the 

 proteins, with which they are bound in the cell. It is possible to obtain aqueous solu- 

 tions of certain enzymes, such as amylase (diastase), protease, and invertase (sac- 

 charase). It has been assumed (Fodor) that yeast invertase is identical with a carbo- 

 hydrate yeast gum but the removal of this gum does not seem to affect the activity 



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