A novel lipoate attachment enzyme is shared by Plasmodium and Chlamydia species

Summary Lipoate is an essential cofactor for enzymes that are important for central metabolism and other processes. In malaria parasites, scavenged lipoate from the human host is required for survival. The Plasmodium falciparum mitochondrion contains two enzymes (PfLipL1 and PfLipL2) that are responsible for activating mitochondrial proteins through the covalent attachment of lipoate (lipoylation). Lipoylation occurs via a novel redox‐gated mechanism that remains poorly understood. We show that PfLipL1 functions as a redox switch that determines which downstream proteins will be activated. Based on the lipoate redox state, PfLipL1 either functions as a canonical lipoate ligase or as a lipoate activating enzyme which works in conjunction with PfLipL2. We demonstrate that PfLipL2 is a lipoyltransferase and is a member of a novel clade of lipoate attachment enzymes. We show that a LipL2 enzyme from Chlamydia trachomatis has similar activity, demonstrating conservation between intracellular pathogens from different phylogenetic kingdoms and supporting the hypothesis that an early ancestor of malaria parasites once contained a chlamydial endosymbiont. Redox‐dependent lipoylation may regulate processes such as central metabolism and oxidative defense pathways. Malaria parasites rely on scavenging the enzyme cofactor lipoate from their human host. Scavenged lipoate is attached to proteins in the parasite mitochondrion using two different mechanisms that differ based on the redox state of the lipoate substrate. Oxidized lipoate is attached to the H‐protein by the lipoate ligase LipL1. Reduced lipoate is adenylated by LipL1 and subsequently transferred to BCDH and KDH by the lipoyl transferase LipL2.