lipoamidecontaining

Lipoamide-containing refers to enzymes or cofactors that bear the lipoamide prosthetic group, a derivative of lipoic acid covalently linked to a lysine residue in lipoyl domains of certain multi-enzyme complexes. The lipoamide moiety acts as a flexible, redox-active arm that cycles between oxidized and reduced states during catalysis and facilitates transfer of acyl groups between catalytic centers.

In key metabolic complexes, such as the pyruvate dehydrogenase (PDH) complex, the α-ketoglutarate dehydrogenase complex, and the branched-chain α-ketoacid dehydrogenase complexes, the lipoyl domain of the E2 subunit carries the lipoamide arm. The arm accepts an acetyl or other acyl group from the E1 subunit to form acetyl-lipoamide, which is then transferred to CoA to generate acetyl-CoA. The reduced form of the lipoyl group is reoxidized by the E3 subunit, dihydrolipoamide dehydrogenase, using FAD and NAD+ as cofactors, thereby regenerating the active lipoamide for further catalytic cycles.

Biosynthesis and attachment of the lipoamide group (lipoylation) occur via dedicated enzymes. In bacteria, lipoyltransferase systems attach lipoate to lysine residues on lipoyl domains, often involving LipB/LipA-like enzymes. In eukaryotes, mitochondrial lipoylation involves distinct enzymes that attach lipoic acid to designated lysines on target proteins. Lipoamide-containing enzymes are essential for linking glycolysis to the tricarboxylic acid cycle and for the oxidation of several key substrates; defects in lipoylation pathways can disrupt energy metabolism and are studied in metabolic disease research.