Xanthine oxidoreductase exists in two functionally distinct forms, xanthine dehydrogenase (XDH, D-form) and xanthine oxidase (XOX, O-form). Under normal conditions, the larger part of the enzyme occurs in an NAD+-dependent dehydrogenase form that produces NADH and urate. The dehydrogenase can be transformed under various (patho)physiological conditions to an oxygen-dependent oxidase which produces reactive oxygen species [...]