COENZYMES DERIVED FROM B VITAMINS 195 



acetyl intermediate, only pantothenic acid is needed to mediate the initial 

 condensation. 



I. Reactions demonstrated using cell-free preparations in which coenzyme A is the 

 cofactor. 



A. Formation of acid phosphates 



acetic acid + ATP — >■ phosphoryl-acetyl intermediate +ADP 



B. Formation of esters 



choline +acetic acid + ATP — > acetylcholine +ADP+H 3 P0 4 260 



C. Formation of amides 



p-aminobenzoic acid (or sulfonamides) + acetic acid -f ATP >■ acetylated 



amine+ADP+HsPCV 56 



D. Condensation reactions* 



2 acetic acid+ATP — >■ acetoacetic acid+ADP+H 3 P0 4 ' ,>D 



II. Conversions requiring pantothenic acid which can be demonstrated in vivo by the 

 use of pantothenic acid antagonists, deficient cells, isotopes, 

 acetic acid — >■ fatty acids (bacteria) 267 - 268 



acetic acid >■ phloroglucinol-like compound (bacteria) 269 



acetic acid — > sterols (bacteria) 267 - 268 



acetic acid >■ aromatic amino acids (bacteria) 269 



acetic acid >■ cz's-aconitate >■ a-ketoglutarate (bacteria) 268 * 



acetic acid — > C0 2 -t-H 2 (yeast) 264 



glucose, or pyruvic acid, or lactic acid — >■ CO2+H2O (rat liver) 270 - 266 (duck 



tissues) 266 (bacteria) 262 - 271 

 proteins or carbohydrates — >■ fats (rat) 272 



III. Conversions involving acetic acid for which pantothenic acid has not yet been 

 shown essential. 



acetic acid >■ formic acid (pigeon) 273 



acetic acid >■ porphyrins (dog) 274 



ketogenic substances >■ acetone bodies (mammals) 



acetic acid+acetic acid — >■ succinic acid (molds) 275 



The synthesis of "fats from either carbohydrate or protein as far as is 

 now known must go on through processes in which reactions mediated 

 by pantothenic acid cause the condensation of reactive acetyl molecules. 

 The pantothenic acid-requiring reactions in which carbohydrates and 

 fats are oxidized and in which fatty acids are synthesized are undoubt- 

 edly essential in many forms of life, while the reactions in which amines 

 and alcohols are acetylated may be of importance only in specific phyla 

 having special functions in which an acetylating agent is needed for the 

 production of acetic acid esters or amides. 



No detailed studies of the possible dissociation of coenzyme A from the 

 apoenzyme while the coenzyme is still associated with the phosphorylated 

 acetic acid have yet been undertaken; hence, it is not known whether 

 (1) both the creation and utilization of the "active acetate" must take 

 place simultaneously in a coupled system, or (2) coenzyme A accepts the 

 active molecule from one enzymatic reaction, dissociates itself from this 



* The reaction in which citric acid is formed by the condensation of an activated 

 acetate with oxalacetate should be added to the well characterized reactions since 

 coenzyme A has now been shown to be the coenzyme which reactivates an aged 

 cell-free preparation capable of accomplishing this synthesis (see footnote p. 223). 



