Reactions Requiring Acyl Activation Frequently Use Phosphopantetheine Coenzymes

Reactions Requiring Acyl Activation Frequently Use Phosphopantetheine Coenzymes 

4 -Phosphopantetheine coenzymes are the biochemically active forms of the vitamin pantothenic acid. In figure 10.11, 4 -phosphopantetheine is shown as covalently linked to an adenylyl group in coenzyme A or it can also be linked to a protein such as a serine hydroxyl group in acyl carrier protein (ACP). It is also found bonded to proteins that catalyze the activation and polymerization of amino acids to polypeptide antibiotics. Coenzyme A was discovered, purified, and structurally characterized by Fritz Lipmann and colleagues in work for which Lipmann was awarded the Nobel Prize in 1953. 

The mechanistic importance of activation is exemplified by the condensation of two molecules of acetyl- 

The two important steps of the reaction depend on both acetyl groups being activated, one for enolization and the other for acyl-group transfer. In the first step, one of the molecules must be enolized by the intervention of a base to remove an a proton, forming an enolate  

Structures of the vitamin pantothenic acid (in red) and coenzyme A. The terminal —SH (in blue) is the reactive group in coenzyme A (CoASH). 

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Reactions Requiring Acyl Activation Frequently Use Phosphopantetheine Coenzymes a-Lipoic Acid Is the Coenzyme of Choice for... 

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