Chapter 2 

 ENZYMES AND ENZYMIC ACTIVITIES OF FUNGI 



Enzymes and catalysts. Enzymes may be defined as organic 

 catalyzers, with specific powers of reaction, that are formed by 

 living cells but are capable of functioning independently of them. 

 This definition conveys a clear concept only if the reader has a 

 working understanding of catalyzers. It has long been known 

 that relatively small amounts of certain substances modify the 

 velocity of chemical reactions. Finely divided platinum, for in- 

 stance, greatly speeds up the decomposition of hydrogen peroxide 

 into water and molecular oxvffen. Alteration of rate of reaction 

 may not always be in the direction of acceleration; it may be in 

 the direction of retardation instead, so that the velocity of reaction 

 may be either accelerated or retarded by catalysts. 



According to the old conception, catalysts are mysterious 

 chemical substances which are unable to initiate a reaction but 

 can change the rate of one already in progress; they do not appear 

 in the end-products, nor are they used up during the reaction. 

 From the newer viewpoint catalysts are to be regarded as sources 

 of surface energy. They are capable of functioning provided 

 that the spatial configuration of atoms in the surface of the 

 catalyst is such as to cause certain oriented adsorption relation- 

 ships, thus permitting the catalyst to contribute surface energy to 

 the system. Presumably this surface energy induces electron dis- 

 placements in the adsorbed and oriented molecules, which are, 

 as a result, chemically active. If in catalysis surface-energy forces 

 and oriented adsorption are the important features, it can be 

 understood that diverse chemicals can be used to catalyze a 

 given reaction. Such a concept, moreover, affords a logical ex- 

 planation for believing that catalysts, by inducing electron shifts 

 in the reacting molecules, may themselves initiate reactions. 



According to this newer conception, even though the catalyst 

 may not actually appear in the end products of the reaction, the 



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