Lipoamide dehydrogenase is a component of the glycine decarboxylase (GDC) or glycine cleavage system as well as of the alpha-ketoacid dehydrogenase complexes. LPD1 is probably the protein most often associated with the glycine decarboxylase complex while LPD2 is probably incorporated into alpha-ketoacid dehydrogenase complexes. (R)-N(6)-dihydrolipoyl-L-lysyl-[protein] + NAD(+) = (R)-N(6)-lipoyl-L-lysyl-[protein] + H(+) + NADH Binds 1 FAD per subunit. Homodimer (By similarity). Part of both the glycine cleavage system composed of four proteins: P, T, L and H and of the pyruvate dehydrogenase complex containing multiple copies of three enzymatic components: pyruvate dehydrogenase (E1), dihydrolipoamide acetyltransferase (E2) and lipoamide dehydrogenase (E3). Preferentially expressed in leaves, flowers and siliques and at a lower level in roots and stems. Up-regulated by light. S-nytrosylated at unknown positions. The active site is a redox-active disulfide bond. Belongs to the class-I pyridine nucleotide-disulfide oxidoreductase family. Truncated N-terminus.