Phosphopantetheine

4'-Phosphopantetheine is an essential prosthetic group of acyl carrier protein (ACP) and peptidyl carrier proteins (PCP) and aryl carrier proteins (ArCP) derived from Coenzyme A. It is also present in formyltetrahydrofolate dehydrogenase.

Functions
Phosphopantetheine fulfills two demands.
 * First, the intermediates remain covalently linked to the synthases (or synthetases) in an energy-rich thiol ester linkage.
 * Second, the flexibility and length of phosphopantetheine chain (approximately 2 nm) allows the covalently tethered intermediates to have access to spatially distinct enzyme active sites.