Turkey liver xanthine dehydrogenase. Relation between nicotinamide-adenine dinucleotide oxidoreductase activity and the content of functional enzyme.

The turkey liver xanthine dehydrogenase-catalysed oxidation of NADH by Methylene Blue, by ferricyanide or by O2 is not dependent on the integrity of the active-centre persulphide groups. By contrast, the NADH-dichlorophenol-indophenol oxidoreductase and NADH-trinitrobenzenesulphonate oxidoreductase activities are directly proportional to the content of functional enzyme. These findings help to identify the sites of egress of electrons to oxidizing substrates.