38 ENZYMES AND ENZYMIC ACTIVITIES OF FUNGI 



catalytic surface may have entered into the reaction, or there 

 may have been an oriented adsorption at the catalyst's surface 

 with the result that the reacting molecules are brought within the 

 sphere of chemical attraction and reactivity. If then the products 

 of the reaction are attracted to the reacting materials more strongly 

 than to the catalyst, there is a continuous migration from the 

 catalyst to the reacting materials until the transformation has been 

 completed. 



Within certain limits the degree of acceleration of a reaction is 

 proportional to the concentration of catalyst present, although 

 the final equilibrium is entirely independent. With a smaller 

 amount of catalyst, however, a longer time may be required to 

 produce a definite equilibrium. 



Water constitutes one of the most important catalysts known. 

 Its effect is evident in the case of pure chlorine gas and hydrogen 

 gas, which will not combine to form HC1 at a measurable rate 

 except in the presence of water. 



Our knowledge of enzymes begins with the observations of 

 Pay en and Persoz, who in 1833 made the observation that germi- 

 nating seeds contain a substance which transforms starch into 

 sugar. They called this substance diastase, although amylase is 

 the preferred name. This discovery marks the beginning of 

 studies of "organized ferments," which were thought to be the 

 agents that carried on catalytic processes within living cells, as 

 distinguished from "unorganized ferments," which did not re- 

 quire the presence of living cells. Confusion in the use of the 

 word ferment led Kuhne in 1867 to suggest the name enzyme for 

 all organized ferments. The distinction between organized and 

 unorganized ferments completely broke down, how ever, when 

 Buchner in 1897 isolated diastase from yeast. He crushed yeast 

 cells with sand, pressed out a straw-colored fluid, filtered it to 

 free it from living cells or their fragments, and found that the 

 clear fluid was capable of producing alcoholic fermentation. He 

 also demonstrated that this alcohol-forming substance was pre- 

 cipitable by alcohol and easily destroyed by heat. Since then an 

 enormous literature on enzymes has come into existence, much 

 too copious to be summarized in one chapter or even one volume. 

 For brief presentations Waksman and Davison (1926) or Tauber 

 (1937) is very useful, and for a more elaborate summary the set 

 of eight volumes edited by Nord and Weidenhagen (1932-1939) 



