The decarboxylation of phosphopantothenoylcysteine (PPC) to 4'-phosphopantetheine (PPANT) is carried out by phosphopantothenoylcysteine decarboxylase (PPCDC). PPCDC is cytosolic and exists as a homotrimer, binding one FMN cofactor per subunit. While a second isoform has been inferred from large-scale sequnceing studies, it lacks the protein's FMN-binding domain and would thus appear to be nonfunctional if it is expressed.
de Crecy-Lagard, V,
phosphopantothenoylcysteine decarboxylase activity of 3xPPCDC:3xFMN [cytosol]