III. BIOCHEMICAL SYSTEM 



599 



1000 - 



5 500 - 



- 3000 



- 2000' 



- 1000 



Fig. 1. Coenzyme A, the common activator of sulfanilamide acetylation in liver 

 extract and choline acetylation in brain extract.'" A highly purified preparation of 

 CoA was used. 



the acetylation of sulfonamide in liver and for the acetylation of choline in 

 brain were identical.^ An effort was then made to purify the coenzyme more 

 rigorously, and preparations were obtained which appeared to be far 

 enough advanced in purity to justify a chemical study of the product. 



B. IDENTIFICATION OF PANTOTHENIC ACID AS 

 PART OF COENZYME A 



1. CoA9* Assay 



As a convenient assay system for the coenzyme, the sulfanilamide ace- 

 tylation system in liver was used.^" In this enzyme system, sulfanilamide is 

 acetylated in the presence of ATP and acetate. After autolysis of the ace- 

 tone-pigeon hver extract for 3 hours at room temperature, the originally 

 present CoA is completely decomposed. The autolyzed extract serves as 

 apoenzyme for measuring CoA. As a unit of CoA, such an amount was 

 defined as giving a half reactivation of the apoenzyme system under spec- 

 ified conditions. A standard curve obtained with this system is shown in 

 Fig. 2. It may be seen that between 0.5 and 1.5 units the curve is nearly a 



s F. Lipmann and N. O. Kaplan, /. Biol. Chem. 162, 743 (1946). 

 '" F. Lipmann, Advances in Enzijmol. 6, 231 (1946). 



'* The following abbreviations are used: AMP = adenosine monophosphate; ADP = 

 adenosine diphosphate; ATP = adenosine triphosphate; CoA = coenzyme A; P = 

 phosphate; PP = pyrophosphate; and Ac = acetate, acetyl. 

 1° N. 0. Kaplan and F. Lipmann, J. Biol. Chem. 174, 37 (1948). 



