Entry retrieved as a ligand file from the Protein Data Bank at RCSB.

The vitamin precursor of coenzyme A is pantothenate. CoASH is used in biological systems to activate carboxylic acid by converting it into a thioester. The thioester is many times more reactive toward nucleophilic acyl substitution reactions than is the carboxylic acid. Look at the structure shown and write down a structural formula for coenzyme A. The central piece of coenyzme A is pantothenic acid; use the ChemFinder to see the structure of that acid. Note that the thiol function occurs as part of the terminal "decarboxylated cysteine" fragment.