Enzymatic Synthesis of Acetono-CoA, A Competitive Inhibitor of Acetyl-CoA with Citrate Synthase

  • Medhanite Awalom
  • Charles J. Stewart


The synthetic acetyl-CoA analog, acetono-CoA (acetonyldethiocoenzyme A), in which the sulfur atom has been replaced by a methylene group, has been previously synthesized and found to be a competitive inhibitor (KI= 13.2 µM) of acetyl-CoA with citrate synthase. To determine whether the acetono-group would interfere with CoA biosynthesis, a crude preparation of the bifunctional enzyme complex which converts ATP and pantetheine 4’-phosphate to CoA was investigated. Incubation mixtures of the crude complex, ATP, and acetonyldethio-pantetheine 4’-phosphate were prepared. Products and reactants were isolated by DEAE-cellulose column chromatography and peaks were identified by TLC. Enzymatic synthesis of acetono-CoA was verified by establishing its KI (25 µM) in the citrate synthase reaction.

The synthetic acetyl-CoA analog, acetono-CoA (acetonyldethio-coenzyme A, Fig. 1), in which the sulfur atom has been replaced by a methylene group, is a competitive inhibitor of acetyl-CoA in the citrate synthase (EC reaction(l). In addition, acetono-CoA has the unique property of being carboxylated by the acetyl coenzymne A carboxylase (EC system(2). Would the activity of the acetono-group interfere with the normal CoA biosynthetic reaction sequence? This sequence:
  1. (1)

    pantetheine 4’-phosphate + ATP ---> dephospho-CoA + PP

  2. (2)

    dephospho-CoA + ATP ---> CoA + ADP


is catalyzed by the bifunctional coenzyme A synthesizing enzyme complex, 1) pantetheine-phosphate adenyltransferase (EC and 2) dephospho- CoA kinase (EC We investigated the ability of the crude enzyme complex to convert ATP and the pantetheine-phosphate analog, acetonyldethiopantetheine 4’- phosphate to acetono-CoA.


Enzymatic Synthesis Crude Enzyme Preparation Acetyl Phosphate Oxaloacetic Acid Methylene Analog 
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Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • Medhanite Awalom
    • 1
  • Charles J. Stewart
    • 1
  1. 1.Department of ChemistrySan Diego State UniversitySan DiegoUSA

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