Lipoic acid is a covalently bound disulphide-containing cofactor required for function of the pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and glycine cleavage enzyme complexes of <taxon tax_id="562">Escherichia coli</taxon>. Two genes, lipA and lipB, are involved in lipoic acid biosynthesis or metabolism. LipA (represented by this entry) is required for the insertion of the first sulphur into the octanoic acid backbone. LipB functions downstream of LipA, but its role in lipoic acid metabolism remains unclear [<cite idref="PUB00008180"/>].Lipoate synthase (or lipoic acid synthetase) catalyses the formation of alpha-(+)-lipoic acid, required for lipoate biosynthesis.