Catalytic Cycle of Type II 4′-Phosphopantetheinyl Transferases

Polyketides are a diverse class of compounds with significant interest in the pharmaceutical industry. They are synthesized by polyketide synthases (PKSs), which consist of large multienzyme systems. Post-translational modification of acyl-carrier protein (ACP) domains is crucial for PKS and fatty acid synthase function and involves phosphopantetheinyl transferases (PPTases) that attach a 4′-phosphopantetheine (Ppant) moiety from coenzyme A (CoA) to a conserved serine residue on the ACP domain. This modification enables communication between the ACP and other enzymatic domains within the same PKS. In Mycobacterium tuberculosis, PptT is essential for bacillus replication and survival during infection. This study focuses on unraveling the activation mechanism of an ACP domain by PptT. It combines biochemical and structural analyses with advanced molecular dynamics simulations to elucidate the precise mechanism of CoA's Ppant arm transfer onto the ACP domain. The findings from this research contribute to a deeper understanding of polyketide biosynthesis with major implications for anti-TB drug discovery efforts.