PROSTHETIC GROUPS, COENZYMES AND ENZYMES 



et al., since both substances are competitive inhibitors of the 

 alcohol oxidation, and both increase the stability of the DPN- 

 ADH linkage. This may seem surprising at first sight. How- 

 ever, Burton and Kaplan emphasize the similarity in molecular 

 shape of ethanol and hydroxylamine, and assume that both have 



to dissociate off a proton in order to form anions, which in their 



+ 



turn should form addition compounds with the /CHx of the 



pyridine ring. Now, both ethanol and hydroxylamine have a 

 very weak tendency to dissociate off a proton, whereas formic 

 acid certainly dissociates very readily. Considering the re- 

 semblance of the formic acid and the hydroxylamine molecules 



H H 



\ \ 



O O HO 



V V 



we may say that it is not at all surprising that the formate 

 anion can react with the positively charged pyridine. It is 

 much harder to understand how the ADH can cause ethanol and 

 hydroxylamine to form anions so readily as required by Burton's 

 and Kaplan's theory. 



From what has been said above it may be predicted that the 

 activity of coenzyme-enzyme systems is influenced by anions to 

 a greater degree than we would have heretofore believed. Our 

 attention has been far too exclusively focused on the hydrogen 

 ion. A systematic investigation of the salt effects on enzymatic 

 activity will undoubtedly reveal many new and interesting 

 facts. 



The effect of chloride, and other anions, on the oxidation- 

 reduction potential of the ADH-system led us to the idea that 

 a salt-sensitive system with an oxido-reducible cofactor revers- 

 ibly attached to a high molecular carrier might be present in 



305 



