Diaphorases are flavin-containing enzymes that can transfer hydrogen from reduced di- and triphosphopyridine nucleotides, including NADH and NADPH, to various dyes, which reduces the dye. Tetrazolium salts, such as iodonitrotetrazolium (INT, ), are commonly used dyes, as reduction produces a highly colored formazan derivative. The diaphorase from C. kluyveri is a flavin mononucleotide-containing enzyme that has both NADH and NADPH dehydrogenase activities. It has an apparent molecular weight of approximately 24 kDa. This diaphorase cannot use NADH or NADPH to reduce either oxygen or cytochrome c.
