Impairment of Lipoylation Mediated by Bromooctanoate Targets Eukaryotic Amidotransferases

Lipoylation is a post-translational modification in which lipoic acid is attached to specific apoproteins of enzyme complexes, like E2 subunits of dehydrogenases or GcvH of the glycine cleavage system. A defining feature of organisms with a lipoyl-relay system is the presence of amidotransferase activity, which enables the transfer of lipoyl groups attached to intermediary proteins to the E2 subunits. In this study, we characterized the lipoate metabolism of Capsaspora owczarzaki and Plasmodium falciparum. Both organisms utilize amidotransferases in their lipoylation pathways, with the filasterian enzyme playing a key role in lipoate synthesis, while the apicomplexan counterpart, previously considered a lipoyltransferase, is essential in its lipoate salvage pathway. We also discovered that specific structural features and certain conserved domains in eukaryotic amidotransferases can significantly influence their mechanism of action and susceptibility to the lipoate analog bromooctanoate. Overall, this study highlights the metabolic strategies of C. owczarzaki and emphasizes the critical role of amidotransferases as ancestral enzymes in the evolution of lipoate metabolism, suggesting that the lipoyl relay may represent a universal pathway across diverse clades.