PPTentsyymien

PPTentsyymien, or PPT enzymes, are a family of enzymes known as 4'-phosphopantetheinyl transferases (PPTases). They catalyze the post-translational activation of carrier proteins by transferring the 4'-phosphopantetheine moiety from coenzyme A to a conserved serine residue on apo-carrier proteins. This modification converts apo-carrier proteins into holo-carrier proteins that can tether growing substrates in fatty acid synthase (FAS), nonribosomal peptide synthetases (NRPS), and polyketide synthases (PKS).

Two major families exist among PPTases: ACPS-type (Type I) and Sfp-type (Type II). ACPS-type PPTases are typically small, often homotrimeric enzymes with narrow substrate specificity, primarily modifying the acyl carrier protein component of type II FAS systems. Sfp-type PPTases are larger, usually monomeric, and exhibit broader substrate specificity, acting on diverse carrier proteins including PCPs in NRPS and modules in PKS. In some organisms, PPTases are standalone enzymes, while in others they are encoded within PKS/NRPS gene clusters and linked to secondary metabolism.

Biological importance: PPTases are essential for the production of many natural products and for primary metabolism. Without PPTase activity, carrier proteins remain in the inactive apo form, halting biosynthetic pathways. Distribution: PPTases are widespread in bacteria, archaea, fungi, and plants, with diverse roles in lipid metabolism, antibiotic biosynthesis, siderophore production, and the assembly of secondary metabolites.

Applications: in biotechnology and drug discovery, PPTases are used to activate engineered PKS/NRPS systems and to study carrier protein interactions. Ongoing research aims to better map substrate specificities and to harness PPTases for combinatorial biosynthesis and the production of novel compounds.