Xanthinuria (Q40107)

Xanthinuria is a rare autosomal recessive disorder associated with a deficiency in xanthine dehydrogenase (XDH - also referred to as xanthine oxidoreductase, XOR), which normally catalyses the conversion of hypoxanthine and xanthine to uric acid. In humans NAD+ is the electron acceptor and significant activity is confined to liver and intestinal mucosa. Irreversible conversion to oxidase occurs during ischaemia. The preferential accumulation/excretion of xanthine in plasma and urine results from extensive hypoxanthine recycling by the salvage pathway for which xanthine is not a substrate in humans: excess xanthine deriving from guanine via guanine deaminase.