Nucleotide metabolism: gout: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Nucleotide metabolism: gout

Sample item

Allopurinol lowers uric acid in gout by inhibiting which enzyme?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Xanthine oxidase

Xanthine oxidase converts hypoxanthine and xanthine to uric acid. Allopurinol and febuxostat reduce urate production by inhibiting this pathway.

Option by option

  • A. Xanthine oxidase (correct)

    Correct. Xanthine oxidase is the urate-producing enzyme.

  • B. Adenosine deaminase

    Adenosine deaminase deficiency causes a form of SCID.

  • C. Dihydrofolate reductase

    Dihydrofolate reductase is inhibited by methotrexate and trimethoprim.

  • D. Thymidylate synthase

    Thymidylate synthase is inhibited by 5-fluorouracil.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Xanthine oxidase. Xanthine oxidase converts hypoxanthine and xanthine to uric acid.

Why is "Adenosine deaminase" not the answer?

Adenosine deaminase deficiency causes a form of SCID.

Why is "Dihydrofolate reductase" not the answer?

Dihydrofolate reductase is inhibited by methotrexate and trimethoprim.

Why is "Thymidylate synthase" not the answer?

Thymidylate synthase is inhibited by 5-fluorouracil.

What concept does this question test?

It tests Nucleotide metabolism: gout in Biochemistry. Allopurinol and febuxostat reduce urate production by inhibiting this pathway.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Nucleotide metabolism: gout?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.