BUTYRIC AC1D-BUTANOL FERMENTATIONS 39 



C 4 acids are combined with another substance, possibly 

 coenzyme A. 23 - 24 



Role of Coenzyme A in Fatty Acid Activation, The 



suggestion that the intermediates in butyrate metabolism are 

 coenzyme A derivatives was based on the work of Lipmann, 

 Lynen, and others on the role of this cofactor in enzymatic 

 acetylation reactions in animal systems, and on the work 

 of Stadtman and his associates on several reactions catalyzed 

 by CI. kluyveri extracts. 



Coenzyme A had been shown to be required for the acety- 

 lation of sulfanilamide by pigeon liver extracts in a system 

 containing acetate and ATP. 25 Methods for the purifica- 

 tion of coenzyme A had been developed, and the structure 

 of the compound had been studied. Not all the structural 

 details had been worked out at this time, but coenzyme A 

 was known to contain adenosine-5'-phosphate, two addi- 

 tional phosphate groups, pantothenic acid, and thioetha- 

 nolamine in a terminal position. 26 The mode of action of 

 coenzyme A in acetate activation was discovered by Lynen 

 et al., 27 who isolated acetyl coenzyme A from yeast, demon- 

 strated that the acetyl group is attached to the sulfur atom, 

 and showed that acetyl coenzyme A acts as an enzymatic 

 acetylating agent. 



This new information concerning coenzyme A was soon 

 applied to the CI. kluyveri system. Stadtman et al. 28 - 29 

 showed that extracts of CI. kluyveri contain an enzyme 

 called phosphotransacetylase that catalyzes a reversible 

 transfer of the acetyl group from acetyl phosphate to 

 coenzyme A. This enzyme was first detected as an activity 

 that caused a rapid decomposition of acetyl phosphate in 

 the presence of inorganic arsenate ("arsenolysis") and also 

 catalyzed a rapid exchange between the phosphoryl group 

 of acetyl phosphate and orthophosphate. When these reac- 

 tions were found to be completely dependent upon the 



