Lipoamide dehydrogenase is a component of the alpha-ketoacid dehydrogenase complexes (By similarity). This includes the pyruvate dehydrogenase complex, which catalyzes the overall conversion of pyruvate to acetyl-CoA and CO(2). Acts also as component of the glycine cleavage system (glycine decarboxylase complex), which catalyzes the degradation of glycine (By similarity). The 10-megadalton pyruvate dehydrogenase complex contains multiple copies of three enzymatic components: pyruvate dehydrogenase (E1), dihydrolipoamide acetyltransferase (E2) and lipoamide dehydrogenase (E3) and catalyzes the overall oxidative decarboxylation of pyruvate to form acetyl-CoA and CO(2) (PubMed:33567276, PubMed:34836937). Within the complex, pyruvate and thiamine pyrophosphate (TPP or vitamin B1) are bound by pyruvate dehydrogenase E1 subunits alpha and beta and pyruvate is decarboxylated leading to the 2-carbon hydrohyethyl bound to TPP. The E2 component contains covalently-bound lipoyl cofactors and transfers the hydroxyethyl group from TPP to an oxidized form of covalently bound lipoamide, and the resulting acetyl group is then transferred to free coenzyme A to form acetyl-CoA and reduced dihydrolipoamide-E2. Finally, the flavoprotein dihydrolipoamide dehydrogenase (E3) re-oxidizes the lipoyl group of dihydrolipoamide-E2 to form lipoamide-E2 and NADH. A fourth subunit, E3BP, is responsible for tethering E3 in proximity to the core, forming the entire metabolon (Probable). (R)-N(6)-dihydrolipoyl-L-lysyl-[protein] + NAD(+) = (R)-N(6)-lipoyl-L-lysyl-[protein] + H(+) + NADH Binds 1 FAD per subunit. Eukaryotic pyruvate dehydrogenase (PDH) complexes are organized as a core consisting of the oligomeric dihydrolipoamide acetyl-transferase (E2), around which are arranged multiple copies of pyruvate dehydrogenase (E1), dihydrolipoamide dehydrogenase (E3) and protein X (E3BP) bound by non-covalent bonds (PubMed:33567276). The Chaetomium thermophilum PDH complex contains 60 E2 units, 12 E3BP units, about 20 E1 units, and 12 or more E3 units (PubMed:33567276). The units are organized in 1 E2 60-mer, 4 E3BP trimers, about 20 E1 tetramers, and a maximum of 12 E3 dimers (PubMed:33567276). The E3BP trimers are bound inside the icosahedral core with tetrahedral symmetry (PubMed:33567276). The active site is a redox-active disulfide bond. Belongs to the class-I pyridine nucleotide-disulfide oxidoreductase family.