unreviewed

Xanthine oxidoreductase (XOR / XDH-XO)

2 reactions · 1 pathways

Cofactors used

H2O

Clinical / pharmacological. Target of allopurinol and febuxostat; deficiency causes xanthinuria

What it does, reaction by reaction

2 reactions

Purine Degradation (to Uric Acid) Nucleotide Metabolism · Cytosol

step 6 Irreversible/directional

Hypoxanthine → xanthine

Converts Hypoxanthine into Xanthine

› Notes

Xanthine oxidoreductase (XOR) catalyzes hypoxanthine + H2O + oxidized electron acceptor → xanthine + reduced electron acceptor. As xanthine dehydrogenase, XOR can transfer electrons to NAD+; as xanthine oxidase, it transfers electrons to O2, generating superoxide and/or H2O2. The molybdenum cofactor, FAD, and iron-sulfur centers are required.

step 7 Irreversible

Xanthine → uric acid (urate)

Converts Xanthine into Uric acid

› Notes

XOR catalyzes xanthine + H2O + oxidized electron acceptor → uric acid + reduced electron acceptor. This is the terminal oxidation in humans and is effectively irreversible; uric acid is largely deprotonated to monosodium urate in extracellular fluid.

Showing all 2 reactions.

What accelerates and inhibits it

Regulation is pathway-specific, so each context is listed separately

1 entries

Purine Degradation (to Uric Acid)

Listed there as: Xanthine oxidoreductase

Accelerated by

Hypoxanthine/xanthine availability; conversion of dehydrogenase to oxidase can occur with oxidation/proteolysis

Inhibited by

Allopurinol (via oxypurinol), febuxostat, topiroxostat

Hormonal control

No dominant acute hormonal regulation; expression can rise with inflammatory and hypoxic/ischemic stress.

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