Reaction: protein N6-(dihydrolipoyl)lysine + NAD+ = protein N6-(lipoyl)lysine + NADH + H+
For diagram, click here, here or here
Glossary: dihydrolipoyl group
Other name(s): LDP-Glc; LDP-Val; dehydrolipoate dehydrogenase; diaphorase; dihydrolipoamide dehydrogenase; dihydrolipoamide:NAD+ oxidoreductase; dihydrolipoic dehydrogenase; dihydrothioctic dehydrogenase; lipoamide dehydrogenase (NADH); lipoamide oxidoreductase (NADH); lipoamide reductase; lipoamide reductase (NADH); lipoate dehydrogenase; lipoic acid dehydrogenase; lipoyl dehydrogenase
Systematic name: protein-N6-(dihydrolipoyl)lysine:NAD+ oxidoreductase
Comments: A flavoprotein (FAD). A component of the multienzyme 2-oxo-acid dehydrogenase complexes. In the pyruvate dehydrogenase complex, it binds to the core of EC 22.214.171.124, dihydrolipoyllysine-residue acetyltransferase, and catalyses oxidation of its dihydrolipoyl groups. It plays a similar role in the oxoglutarate and 3-methyl-2-oxobutanoate dehydrogenase complexes. Another substrate is the dihydrolipoyl group in the H-protein of the glycine-cleavage system (click here for diagram), in which it acts, together with EC 126.96.36.199, glycine dehydrogenase (decarboxylating), and EC 188.8.131.52, aminomethyltransferase, to break down glycine. It can also use free dihydrolipoate, dihydrolipoamide or dihydrolipoyllysine as substrate. This enzyme was first shown to catalyse the oxidation of NADH by methylene blue; this activity was called diaphorase. The glycine cleavage system is composed of four components that only loosely associate: the P protein (EC 184.108.40.206), the T protein (EC 220.127.116.11), the L protein (EC 18.104.22.168) and the lipoyl-bearing H protein 
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9001-18-7
1. Massey, V. Lipoyl dehydrogenase. In: Boyer, P.D., Lardy, H. and Myrb╠█ck, K. (Eds), The Enzymes, 2nd edn, vol. 7, Academic Press, New York, 1963, pp. 275-306.
2. Massey, V., Gibson, Q.H. and Veeger, C. Intermediates in the catalytic action of lipoyl dehydrogenase (diaphorase). Biochem. J. 77 (1960) 341-351. [PMID: 13767908]
3. Savage, N. Preparation and properties of highly purified diaphorase. Biochem. J. 67 (1957) 146-155. [PMID: 13471525]
4. Straub, F.B. Isolation and properties of a flavoprotein from heart muscle tissue. Biochem. J. 33 (1939) 787-792.
5. Perham, R.N. Swinging arms and swinging domains in multifunctional enzymes: catalytic machines for multistep reactions. Annu. Rev. Biochem. 69 (2000) 961-1004. [PMID: 10966480]
6. Nesbitt, N.M., Baleanu-Gogonea, C., Cicchillo, R.M., Goodson, K., Iwig, D.F., Broadwater, J.A., Haas, J.A., Fox, B.G. and Booker, S.J. Expression, purification, and physical characterization of Escherichia coli lipoyl(octanoyl)transferase. Protein Expr. Purif. 39 (2005) 269-282. [PMID: 15642479]