148 M. E. JONES, S. BLACK, R. M. FLYNN, F. LIPMANN VOL. 12 (1953) 



LiPMANN, HiLZ AND Lynen^^ through the use of iso.topes. The isotope experiments are 

 interpreted to indicate enzyme-bound intermediaries. ATP (Ad-P.^ PP) equihbrates 

 rapidly through yeast enzyme with inorganic ^^P-pyrophosphate in the absence of other 

 components of the system. This seems to imphcate an enzyme-adenosine monophosphate 

 (Ad-P) compound: 



Enzyme + Ad-P ~ PP ^ Enzyme ~ P-Ad + PP (4) 



A subsequent replacement of Ad-P in enzyme ---' P-Ad by CoA is indicated by a 

 reduction of the rate of Ad-P'-^ PP ^ PP-exchange through the addition of CoA: 



Enzyme -- P-Ad + CoA-SH ^ Enzyme ~ S-CoA + Ad-P (5) 



Finally, the same enzyme was found to equilibrate acetyl CoA with free acetate 

 rather easily, although less rapidly than Ad-P^'^PP and pyrophosphate. Such an 

 exchange indicates enzyme '^-' S - CoA to react eventually with acetate to yield the final 

 product, acetyl --^ S - CoA : 



Enzyme ■ — ' S - CoA + acetate ^ Enzyme + acetyl --^ S - CoA (6) 



It is felt that this interpretation furnishes a reasonably good approximation to the 

 final understanding of the mechanism. 



SUMMARY 



The formation of acetyl CoA by interaction of ATP, CoA and acetate has been studied with yeast 

 and pigeon liver preparations. 



Pyrophosphate and AMP have been found to be the products of the reaction, with the formula- 

 tion as follows : 



ATP 4- CoA 4- acetate ^ acetyl CoA 4- AMP 4- pyrophosphate 



Magnesium is a component of the enzyme system. 



The reaction is reversible as shown by the conversion of acetyl CoA, pyrophosphate and AMP, 

 to ATP and free CoA. The reversion specifically requires pyrophosphate. 

 Enrichment of the yeast enzyme is described. 



RESUME 



Les auteurs ont etudie la formation d'acetyl CoA par interaction entre I'ATP, le CoA et I'acetate 

 chez des levures et dans des preparations de foie de pigeon. 



La reaction conduit au pyrophosphate et a I'AMP. EUe peut se formuler ainsi: 



ATP 4- CoA 4- acetate ^ acetyl CoA 4- AMP 4- pyrophosphate 



Le magnesium est un constituant du systeme enzymatique. 



La reaction est reversible ainsi que le montre la transformation de I'acetyl CoA, du pyrophos- 

 phate et de I'AMP en ATP et CoA libre. Le renversement de la reaction exige sp^cifiquement du pyro- 

 phosphate. 



Une purification partielle de I'enzyme de la levure est decrite. 



ZUSAMMENFASSUNG 



Die Bildung des Acetyl-CoA bei der Reaktion mit ATP, CoA und Acetat wurde mit Hefe und 

 Taubenleberpraparaten untersucht. 



Es wurde gefunden, dass Pyrophosphat und AMP die Produkte der Reaktion sind, die sich wie 

 folgt formulieren lasst: 



ATP 4- CoA + Acetat ^ Acetyl CoA 4- AMP 4- Pyrophosphat 



Magnesium ist ein Bestandteil des Enzymsystems. 



Die Reaktion is rcversibel, wic durch die Umwandlung von Acetyl-CoA, Pyrophosphat und AMP 

 in ATP und freics CoA gezeigt wurde. Die Umkehr erfordert die Gegenwart von Pyrophosphat. 

 Die Anreicherung von Hcfeenzym wird beschrieben. 



References p. i4g. 



