Coenzyme A

Cross references:   Cholesterol      Cholesterol Synthesis    

Coenzyme A - Wikipedia   
Coenzyme A (CoA, CoASH, or HSCoA) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All genomes sequenced to date encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it (or a thioester, such as acetyl-CoA) as a substrate. "  

Coenzym A.svg


In all living organisms, Coenzyme A is synthesized in a five-step process that requires four molecules of ATP, from pantothenate and cysteine:[2]

  1. Pantothenate (vitamin B5)

Skeletal formula of (R)-pantothenic acid

  1. is phosphorylated to 4'-phosphopantothenate by the enzyme 

  2. pantothenate kinase (PanK; CoaA; CoaX)

  1. A cysteine

L-Cystein - L-Cysteine.svg

  1.  is added to 4'-phosphopantothenate by the enzyme

  2. phosphopantothenoylcysteine synthetase (PPCS; CoaB) to form

  3. 4'-phospho-N-pantothenoylcysteine. 

  1. PPC is decarboxylated to

  2. 4'-phosphopantetheine by 

  3. phosphopantothenoylcysteine decarboxylase (PPC-DC; CoaC)

  1. 4'-phosphopantetheine is adenylylated to form dephospho-CoA by the enzyme

  2. phosphopantetheine adenylyl transferase (PPAT; CoaD)
  3. Finally, dephospho-CoA is phosphorylated to coenzyme A by the enzyme

  4. dephosphocoenzyme A kinase (DPCK; CoaE). 

        ATP + dephospho-CoA \rightleftharpoons ADP + CoA   

Enzyme nomenclature abbreviations in parentheses represent eukaryotic and prokaryotic enzymes respectively. In some plants and bacteria, including Escherichia coli, pantothenate can be synthesised de novo and is therefore not considered essential. 

Thiol - Wikipedia  

Thioester - Wikipedia