Lipoic acid salvage and biosynthesis pathways. α-Lipoic acid is generated and attached to the E2-subunit of KADH or the H-protein of GCS bytwo mechanisms. In E. coli and eukaryotes (including Plasmodium), LipB transfers the octanoyl-moiety from Oct-ACP directly to the lipoyl-domain of E2 andtwo sulphurs are subsequently introduced by LipA. In B. subtilis the LipB homologue LipM transfers the ocantoyl-moiety to the H-protein of the bacterialGCS. Octanoylated GCS-H protein is the substrate for the transamidase LipL, which transfers the octanoyl-moiety to the lipoyl-domain of the E2-subunitwhich is followed by the introduction of the sulphurs via LipA. It is not fully understood if LipA functions before or after the action of LipL. Salvage of α-lipoic acid is achieved through the activity of two proteins (lipoate activating enzyme and lipoyltransferase) in mammals while E. coli (and Plasmodium) onlyrequires the activity of LplA to catalyse the ligation of free α-lipoic acid to the lipoyl-domain of the E2-subunit of KADH or the H-protein of the GCS. In L.monocytogenes, LplA1 catalyses the ligation of α-lipoic acid to the GCS-H-protein before it is transferred by LipL to the E2-subunit of the KADH.