Question 16 of 16
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Allopurinol is an inhibitor of xanthine oxidase. Administration of allopurinol to a patient with gout and normal HG-PRT levels would be expected to lead to all of the following EXCEPT:
The correct answer is (D).
- A. decreased de novo synthesis of IMP.
- B. decreased urate in the urine.
- C. an increase of hypoxanthine in the blood./a>
- D. increased levels of PRPP .
- E. tincreased xanthine in the blood.
- A. As long as HG-PRT is available, the increased xanthine and hypoxanthine will be salvaged to GMP and IMP, both of which inhibit the rate limiting step of the synthesis..
- B. Allopurinol directly inhibits the production of urate.
- C. Hypoxanthine is a substrate for the inhibited enzyme and, therefore, increases.
- D. As long as HG-PRT is available, the increasing xanthine and hypoxanthine will consume PRPP. Contrast this to the situation with the Lesch-Nyhan syndrome.
- E. Xanthine is a substrate for the inhibited enzyme.
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Last modified 1/5/95