Lipoamide dehydrogenase is a component of the alpha-ketoacid dehydrogenase complexes (By similarity). Malfunction of this protein blocks the progression of cell cycle from G1 to S phase. (R)-N(6)-dihydrolipoyl-L-lysyl-[protein] + NAD(+) = (R)-N(6)-lipoyl-L-lysyl-[protein] + H(+) + NADH Binds 1 FAD per subunit. Homodimer. The active site is a redox-active disulfide bond. Belongs to the class-I pyridine nucleotide-disulfide oxidoreductase family.