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. It is adapted from cysteamine, pantothenate, and adenosine triphosphate.

Biosynthesis

Coenzyme A is synthesized in a five-step process from pantothenate:

1. Pantothenate is phosphorylated to 4'-phosphopantothenate by the enzyme pantothenate kinase
2. A cysteine is added to 4'-phosphopantothenate by the enzyme phosphopantothenoylcysteine synthetase to form 4'-phospho-N-pantothenoylcysteine (PPC)
3. PPC is decarboxylated to 4'-phosphopantetheine by phosphopantothenoylcysteine decarboxylase
4. 4'-phosphopantetheine is adenylylated to form dephospho-CoA by the enzyme phosphopantetheine adenylyl transerase
5. Finally, dephospho-CoA is phosphorylated using ATP to coenzyme A by the enzyme dephosphocoenzyme A kinase.

Function

Since coenzyme A is chemically a thiol, it can react with carboxylic acids to form thioesters, thus functioning as an acyl group carrier. It assists in transferring fatty acids from the cytoplasm to mitochondria. A molecule of coenzyme A carrying an acetyl group is also referred to as acetyl-CoA. When it is not attached to an acyl group it is usually referred to as 'CoASH' or 'HSCoA'.

List of coenzyme A activated acyl groups

• Acetyl-CoA
• Propionyl-CoA
• Acetoacetyl-CoA
• Coumaroyl-CoA (used in flavonoid and stilbenoid biosynthesis)
• Acyl derived from dicarboxylic acids
  • Malonyl-CoA
  • Succinyl-CoA
  • Hydroxymethylglutaryl-CoA (used in isoprenoid biosynthesis)
  • Pimelyl-CoA (used in biotin biosynthesis)

• Butyryl CoA

Additional images

References

• Karl Miller (1998). Beta Oxidation of Fatty Acids. Retrieved May 18, 2005.
• Charles Ophard (2003). Acetyl-CoA Crossroads. Retrieved May 18, 2005.
• Lehninger: Principles of Biochemistry, 4th edition, David L. Nelson, Michael M. Cox
• http://www.elmhurst.edu/~chm/vchembook/621fattyacidrx.html