Diaphorase or dihydrolipoyl dehydrogenase is a flavoprotein enzyme capable of oxidizing the reduced form of NAD (NADH). This lipoamide dehydrogenase is a component of the glycine cleavage system, as well as of the alpha-ketoacid dehydrogenase complexes. It binds one FAD per protein subunit. The enzyme is provided in 3.2 M ammonium sulphate.