Multiple choice

Trimethoprim is an effective inhibitor of bacterial growth due to which of the following reasons?

  1. It is a competitive inhibitor of dihydropteroate synthase.

  2. It has an affinity for bacterial dihydrofolate reductase (DHFR).

  3. It blocks the synthesis of dihydrofolic acid.

  4. It is a non-competitive inhibitor of dihydrofolic acid and reduces its activity.
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B Correct answer
Explanation

Trimethoprim has a very high affinity for bacterial dihydrofolate reductase. It competitively inhibits the activity of DHFR and inhibits the reduction of dihydrofolic acid (DHF) to tetrahydrofolic acid (THF). THF is an essential precursor in the thymidine synthesis pathway and interference with this pathway inhibits bacterial DNA synthesis.

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