Allopurinol treats gout by inhibiting xanthine oxidase. This results in accumulation of which metabolites that are more soluble than uric acid?

• A Adenosine and guanosine as the purine degradation pathway backs up
• B Allantoic acid and allantoin produced by an alternate oxidation pathway
• C Inosine monophosphate (IMP) and GMP accumulate in joints
• D Hypoxanthine and xanthine, which are more water-soluble than uric acid ✓

Explanation

Xanthine oxidase converts hypoxanthine to xanthine, and xanthine to uric acid. Allopurinol inhibits this enzyme, causing accumulation of hypoxanthine and xanthine, which are significantly more water-soluble than uric acid and less likely to precipitate in joints and tubules. A rare complication of allopurinol is xanthine nephropathy if xanthine accumulates excessively. Allopurinol is itself metabolised to oxipurinol, the active inhibitor. Allantoin is produced by uricase in non-human mammals.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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