caffeoylCoA

Caffeoyl-CoA is the coenzyme A thioester of caffeic acid, an activated intermediate in phenylpropanoid metabolism. It is typically formed from caffeic acid by 4-coumarate:CoA ligase (4CL), which uses ATP and CoA, though other CoA ligases can also generate caffeoyl-CoA in alternative pathways. As an activated hydroxycinnamate, caffeoyl-CoA serves as a substrate for a variety of enzymes that channel flux into lignin biosynthesis and related phenolics.

In plants, caffeoyl-CoA is implicated in the formation of lignin monomers and other hydroxycinnamate derivatives. Through subsequent methylation and reduction steps, caffeoyl-CoA can be converted into feruloyl-CoA and related intermediates that feed into the production of coniferyl and sinapyl alcohols, contributing to guaiacyl and syringyl lignin units. It also participates in chlorogenic acid biosynthesis, where the caffeoyl moiety can be transferred to quinic acid by specific transferases to form chlorogenic acids. Additional enzymes, such as caffeoyl-CoA O-methyltransferase (CCoAOMT) and caffeic acid O-methyltransferase (COMT), modify the hydroxycinnamoyl moieties, influencing the spectrum of downstream phenolics.

In microorganisms, caffeoyl-CoA and related esters can appear in pathways for degradation or transformation of caffeic acid, enabling catabolism or remodeling of hydroxycinnamates. Overall, caffeoyl-CoA functions as a central, high-energy intermediate that enables the biosynthesis and diversification of plant phenolics, including lignins, lignans, chlorogenic acids, and related compounds.